By Luis A Bate Fall 2011
1. Nervous System
Specialized cells detects signs from internal and external environments
Inputs are consciously recognized OR dealt with on an unconscious level
Within the central nervous system
Sensory input is processed and outcome is decided upon
Outcome: active response, stored as memory, discarded as not imp (70%)
Control of muscles and glands
After NS stimulation, most skeletal muscle contracts
Skeletal muscle movements: Reflex and Voluntary
Smooth muscle movement due to: hormone action OR direct nervous impulses
Most nervous sys actions are aimed at maintaining homeostatic conditions
Nervous sys coordinated cell synchronization of the body
Thinking, Storing & Recalling memories
Generating emotional responses, state of awareness or consciousness
Structure and Divisions of the Nervous System
Contains brain and spinal cord
Contains multipolar neurons
Highly branched dendritic terminal and a single axon
Receives information from bipolar and monopolar neurons
Bipolar have one dendritic process and one axon
Monopolar are sensory neurons
Characterized by: protective covering of multilayer connective tissue called meninges
Supported by: Glial Cells
Physical support to neurons via the blood brain barrier
Provide conduit for the transfer of nutrients
Contributes to the removal of debris via phagocytosis
Epithelial cells lining the ventricles of the brain, filled with CSF
Responsible for the circulation & production of CSF
Located in choroid plexus
Act as macrophages, providing immune protection
Provide support to axon bundles via myelin sheaths
Brain (12 pairs of cranial nerves)
Cerebrum / Telecephalon (2 pairs of cranial nerves from brain connect here)
Largest component of the brain
Grey matter (unmyelinated neurons)
Responsible for memory, awareness, perception, language, counciousness, and thought
White matter (myelinated neurons)
Made up of nervous tracts connecting different areas of the brain and the rest of the CNS
Two hemispheres & several lobes
Motivation, aggression, mood, voluntary motor activity, some senses of smell
Vision sensory information
Smell & hearing sensory information
Remaining sensory information
located between brainstem and cerebrum
Sensory, except smell, relay of the brain (from synapse to cortex)
Emotional processing, which influences sensory integration
Lowest component, containing variety of nuclei & nervous tracts
Some involved in responding to olfactory stimulus
involved in controlling and regulating endocrine system
(in conjunction with hypophysis)
Pineal Gland: influences several biological rhythms (activity)
Habenular Nucleus: participates in innate response to odor
Interacts with brainstem and CNS
Purkinje cells (most complex cells in cerebellum)
Responsible for eye movement, posture, locomotion, & fine motor coordination. Cerebellum and frontal lobe (cerebral cortex) are responsible for learning complex movements
Brainstem (9 pairs of cranial nerves from brain connect here)
movement of head, body, & eyes,
in response to sound, texture, & sight
Relay for information between cerebrum and cerebellum
+ some components of sleep & resp. center of medulla
Each aspect controlled by different nuclei
Conscious control or skeletal muscle (control balance)
Nerve fibers cross from one brain hemisphere to the opposite side of the PNS
Contains several nuclei distributed throughout the brainstem which regulate / control some cyclic activity (e.g. wake-sleep)
Spinal Cord (1 pair of cranial nerves from brain connect here)
Links brain to peripheral nerves
Conducts regulatory activity through reflexes
Extends from foramen magnum to the 2nd lumbar vertebra
31 pairs of spinal nerves connect to different tissues & organs
8 cervical, 12 thoracic, 5 lumbar, 6 sacral (includes coccygeal nerves)
Contains all components outside CNS (ganglia, plexuses, sensory receptors…)
Glial Cells of PNS
Schwann cells / Neurolemmocytes
Myelin sheath on one axon providing insulation
Sensory ganglia: support, nutrition, & protection of cell bodies
Stimulus (trigger) initially causes a graded (local) potential which then must reach threshold to generate a depolarization
Potentials: events and consequences
Ion channel open |increased permeability to Na+,K+,Cl-
Increased Na+ |depolarization
Increased K+ / Cl- |hyperpolarization
Several graded potentials |summate
Graded potential |spread with decreased strength
Depolarization |action potential
Intensity of a
stimulus is determined by:
Frequency code |number of APs/ unit of time (Hz)
1 Hz = 1 stimulus / second
Population code |density of receptors in the area
Sensitivity |population code x area/size covered
Single process leaving the cell body which branches into two components, one with a dendritic end and one with a synaptic bulb
Bodies located in the dorsal root ganglion
connects CNS to skeletal muscle
character: cell bodies have all its neurons in CNS (spinal cord) axons leave spinal cord via ventral root and connects directly with a given skeletal muscle.
Involuntary or subconscious caring for ongoing functions of organism
contains two neurons between CNS and effecter organ
Axon leaves via ventral root and synapses with another neuron in an autonomic ganglion onto the body of a second motor neuron which synapses with the effecter organ.
Enteric nervous system
2. Muscle Receptors and Spinal Reflexes
Largest → Smallest
- Roman numbered
nerves I-IV have
I having the largest
- A = myelinated
- C = unmyelinated
- Within A:
α = larger and faster
γ = smaller and slower
Intrafusal muscle fibers
Make up muscle spindles (fusiform shape)
Spindle is innervated at poles by Aγ motor neurons
Non-contractile section in the middle of spindle is innervated by afferent sensory fibers Ia (rate/ speed of stretch) & II (amount of stretch, non-adaptive = APs of info are still sent after muscle had finished streching)
Fibers are located within the muscle but are isolated by a collagen sheath
Function to detect the amount & rate of changes in muscle length
Extrafusal muscle fibers
Innervated by Aα motor neurons
In charge of causing muscle contraction
Reflex Arc (simplest functional unit of NS)
Action: to perform an automatic response, without conscious thought
Consists of: sensing a stimulus, and generating the appropriate responmse
Receptor detects stimulus & converts it to an AP
neuron conveys AP through cell body (dorsal root ganglion SC) &
through the Axon (dorsal horn Spinal Cord) & synapses
Interneuron connects the sensor neuron to the motor neuron, stays in SC
Motor neuron exits SC through ventral root, synapses on effecter organ
Effecter organ organ effected by motor neuron
Types of Reflexes
Monosynaptic Reflexes = without interneurons
Segmental Reflex = Include small segment of the CNS
Intersegmental Reflex = Include integration in the SC & Brain
usually activated by proprioreception
usually activates multiple neurons (active/inhibitory)
Monosynaptic or Polysynaptic
Contract a muscle that is being stretch to prevent overstretching of muscle
3-10 specialized skeletal muscle fibers make up muscle spindle
maintenance of steady standing posture &
to coordinate muscle movement
Sensory neurons at the center of muscle spindle, carries AP to the SC where it synapses with Aα motor neuron which sends AP to the muscle where the spindle is located to contract (and prevent further stretching)
Aγ motor neurons around spindle regulates the spindle sensitivity by shortening the spindle itself and matching the tension with the muscle.
Golgi tendon Reflex:
Prevents contracting muscle from causing damage to the tendon
Acts as a sensory receptor, which is located within the tendon close to the junction between the muscle and the tendon
As the muscle
shortens, the tendon stretches
If the stretch is severe enough, the golgi tendon reflex send AP to the spinal cord where is connects to the brain and to an inhibitory interneuron.
This then synapses with Aα motor neuron, inhibiting its function, causing a relaxation of the contracted muscle = reducing tension on tendon.
Withdrawal or flexor Reflex:
Remove apex or area from noxious stimulus
triggers a sensory neuron which sends an AP to the SC.
There it stimulates stimulatory interneurons which synapse onto Aα which causes muscle contractions to move limb or body part away from stimulus.
Reciprocal innervations: In many cases, collateral axons (of the sensory neurons) synapse with inhibitory interneurons in the SC, which innervate extensor muscles of that limb.
There is also the crossed extensor reflex, which allows a collateral axon to stimulate muscles of the unaffected limb to help reduce load of keep balance.
Pressure & Locomotion:
Separated into 2 large categories
○ Group of upper ○ Group
motor neurons of upper
○ Originate in cerebral motor
cortex & pass through neurons
Medulla, to synapse
on lower motor
○ Tract1 synapses in SC
○ Tract2 synapses in
brainstem, & goes to
muscle of the head
Differentiation between upper & lower motor neuron disease
• CNS damage • Damage to the Axon
• SC damage shows weakness caudal • There may also be loss of sensory capacity
to damaged area.
3. Special Senses
Sense of Hearing
Sound (in the form of sound waves) reach the external ear
First the Pinna funnels them into the Ear canal
At the end of the ear canal, the sound waves impact the tympanic membrane (eardrum)
The tympanic membrane is connected to the middle ear auditory ossicles
The vibrations, of sound waves, on the tympanic membrane travels to the auditory ossicles where they are amplified and sent to the oval window (opening to the inner ear)
Auditory ossicles = series of 3 small bones
Malleus, incus, stapes
Tympanic memb.(attaches to)→Malleus→incus→stapes→oval window
Middle ear = air filled space
connects to the pharynx by pharyngotympanic tube / Eustachian tube
connection permits equalization of atmospheric & middle ear pressure
equalization prevents vibration distortion of tympanic membrane
Made up of tunnels and chambers (bony labyrinth) located within the temporal bone
Filled with Perilymph
High in sodium, low in potassium (like Cerebral Spinal Fluid)
Surrounds Membranous Labyrinth
Semicircular Canals (balance)
Filled with Endolymph
Low in sodium, high in potassium (like intracellular fluid)
Basilar membrane (one of the membranes making up labyrinth)
to the oval window (vibrates at higher freq.)
& wider at the helicotrema (vibrates at lower frequency)
= apex of cochlea
Supports Hair cells:
Detect the frequency of vibration
Stereocilia: exposed to endolymph in the cochlear duct
→ synapses in the medulla & in the midbrain
→ then connects to the thalamus
→ then connects to the auditory cortex (integration)
located in the dorsal temporal lobe
Sound Pathway (vibrations) of inner ear:
window→ Perilymph vibration→ Endolymph vibration
→ deforms Basilar membrane→ bending of hair cells
→ Potassium channels open→ Potassium enters Stereocilia
→ Stereocilia depolarization→ AP travels down cochlear nerve
Cellular Layer of the Retina (sensory organ)
Rests directly in the choroids
Composed of a single layer of melanin filled cells
Role: to provide
a black matrix that prevents scattering of
light within the eye and isolates individual photoreceptors.
Neural Layer (towards the lumen of the eye)
Located closer to the pigment layer
in the range of visible light
Rods: Cylindrical photosensitive terminal
Black, white, & low light intensity vision
Photoreceptor molecule: rhodopsin
Not present in fovea
Cones:Conical photosensitive terminal
Colour, high light intensity, & visual acuity
Photoreceptor molecules: iodopsin or photopsin
concentration in fovea & macula
& less densely located in the rest of the retina
Bipolar layer (bipolar, horizontal, amacrine
Ganglionic layer (ganglion cells)
Generation of AP (Mechanism used to convert light into an AP by photoreceptor cells)
Photosensitive portion of photoreceptor has hundred of bi-layered, membranous disks
Within the disk are photoreceptive molecules
Rhodopsin: Purple pigment (in rods), Composed of:
Scotopsin: (specific opsin for rhodopsin)
Protein with 7 trans-membrane domains
Retinal: Yellow pigment derived from Vitamin A
The Base of which binds a G-Protein Complex
Gated Na+ Channels: open when bound to cGMP (no light stimulation)
constantly leaking into cell (& is actively pumped
This keeps cell depolarized at a membrane potential of -30mV
Depolarization causes continuous Neurotransmitter (Glutamate) release
Glutamate inhibits bipolar cells from releasing their Neurotransmitter
This leaves inactivated ganglionic cells which send no AP to the Optic n.
In the presence of light: Signal Transduction
changes its configuration
→ Forcing the Scotopsin to change its shape, activating a G-protein
→ This activates a cGMP phosphodiesterase enzyme
→ The enzyme begins converting cGMP to GMP
→ Whithout the cGMP to keep the Na+ channel open, it closes
→ The ATPase removing Na+ continues working, causing the
membrane potential to become more negative → hyperpolarizing
→ Hyperpolarization reduces the amount of glutamate being released
→ The reduction in glutamate, stops inhibiting the bipolar cell
→ Bipolar cells can then release their Neurotransmitter
→ Thus stimulating the ganglionic cell to generate an AP
→ The AP is conveyed by the optic nerve to the CNS
AP from the retina to the optic nerve occur at a rate of 20-25/s
Pathways by neurons involved in vision
A ganglion cell
could integrate the information from 30-60 photoreceptor
Except in the Fovea & Macula where most cells are innervated by a singe ganglion
The Visual Field is separated by a nasal and temporal field (for each eye)
Each field has its own innervation
The axons of the ganglions in the nasal field, reach the optic chiasm & cross
The axons in the temporal field no not cross
All axons synapse in the Thalamus.
From there axons of the thalamic neurons connect to the visual cortex (posterior brain)
Left eye temporal
vision field + Right eye nasal field
→ integrated in the visual cortex of the Left Hemisphere of the brain
temporal vision field + Left eye nasal field
→ integrated in the visual cortex of the Right Hemisphere of the brain
Assessment of vision
The Pupil is controlled by both parasympathetic & sympathetic innervations
Parasympathetic = constrict / Sympathetic = dilate
The stimulus is the amount of light entering the eye (ambient = partially constricted)
Pupillary Light Reflex
Reduction of the diameter of the pupil when light increases in intensity
Consensual Response= When one eye is illuminated, both pupils should constrict
one eye goes to the midbrain, where it is processed
In response, efferent motor neurons send signals to both eyes
Tests of this reflex can be done to evaluate:
Sensory & Motor function of the eye
Brain stem function (where the information is processed)
construction (L) + no construction of non-illuminated eye (R)
= motor neuron problem of non-illuminated eye (R).
(L) = both eyes constrict
+ Illumination of the other eye (R) = neither constrict
= sensory neuron problem of the R eye
The eye of humans can see between frequencies of 380-750nm in the visible light range
The ability to distinguish color is determined by the amount of cones in the Retina
Each cone responds to a specific frequency
Many animals (especially nocturnal hunters) compensate for the color deficiency with the ability to see under low light intensity.
A reflective layer in the retina
This scatters reflected light onto the photoreceptors.
By doing so they also reduce the acuity of vision (reduced ‘sharpness’)
4. Vestibular System
The Functional Anatomy of the Vestibule (Located within the bony Labyrinth)
The vestibular apparatus works with proprioceptors (throughout the body) to gather information regarding the position of the head and the body in order to maintain balance.
linear acceleration of body, using Gravity
Contains: Utricle and Saccule
Most of the
lining of these structures
is covered in cuboidal epithelium
Except for small patch (2-3mm)
which is covered by the macula
of the head &
initial speed of movement
Contains: 3 semi
positioned in 3 different plains at right angles of each other
Horizontal, Frontal, Sagital
Recognizing Posture & Movement
Posture is detected by The Macula (in utricle & saccule of static labyrinth)
Composed of: specialized hair cells (same as in cochlea)
Each hair cell is connected to neurons that will form the vestibular nerve.
They contain many
stereocilia (microvilli) and one large kinocilum.
Stereocilia increase in height towards the kinocilium
The tip of each
stereocilia is connected to a potassium channel by a filament
the filaments attach to adjacent larger stereocilia, leading to the kinocilium
When the stereocilium are displaced (towards the kinocilium), the Potassium channels open: allowing large numbers of positive ions to enter the cells, depolarizing the hair cells. Opposite movement causes hyperpolarization.
All hair cells of the macula are covered by a gelatinous mass
Composed of otoliths or statoconia (protein and calcium carbonate)
Otoliths respond to gravitational force by moving the gelatinous mass
The hair cells in the Macula are positioned in every which way
To detect all possible head positions & any linear accelerations:
Macula in the Utricle is positioned horizontally (side to side)
Macula in the Saccule is positioned vertically (up & down)
Movement: Angular Acceleration / Rotation (in 3 semicircular canals of Kinetic L.)
Ampulla: enlargement at one end of each semicircular canal
Crista ampullaris: specialized structure within ampulla
Contains: hair cells that are all positioned in the same direction
Bending the hair cells depolarizes the membrane and icr. Freq. of AP
Covering the hair cells is the Cupula (gelatinous mass without otoliths)
Cupula is moved by the endolymph within the semi circular canals
Moving the head
sideways (horizontal semicircular canal):
The inertia of the endolymph keeps the fluid in place (relative to the environment), moving the cupula in the opposite direction.
If the movement continues: then the endolymph reaches the same speed of the movement of the head, causing the cupula to return to its normal position & stop signaling.
As soon as the movement of the head diminishes the inertia of the fluid bends the hair in the direction of the initial movement. This causes the hyperpolarisation of the hair cells.
After the fluids settle down the hair cells start depolarizing at the tonic rate.
canals contribute to balance by sensing a rotation & sending
signals to anticipate the reactive movements required to maintain
(which the macula of the utricle and saccule cannot determine rotation until it is too late)
The integration of all this information is done in the midbrain and the cerebellum.
canals are also connected to the eyes:
so the animal can maintain its focus on an object while in movement or rotating the head
This is achieved by sending information which enables rotation of the eyes in an equal but opposite direction to the rotation of the head.
All this control is done through reflexes integrated in the vestibular nuclei and the oculomotor nuclei of the medulla oblongata.
Common Pathologies associated with Balance Problems - Vestibular Disease
5. Cerebellum Caudal to the Cerebral Cortex
Contributes to ~10% to the brain’s weight, & Contains more than half of all the neurons in the brain.
Functions to coordinate and fine-tune movements initiated in other areas of the brain.
It adjusts the outputs of the pyramidal and extrapyramidal system.
- It also functions to read and readjust any current movement, with the intended ones
The cerebellum integrates & compares all the information from muscle spindles, the visual system, the vestibular system, and many other movement receptors. If the movement is not as intended, it sends motor efferent signals to correct it
Structures & Their Role
Located in the flocculonodular lobe (posterior ventral area)
Collects inputs from the visual and vestibular system
Processes the information & Sends efferent output to the vestibular nuclei
Function: to regulate balance as well as head and eye movement.
Located in the medial portion of the cerebellum
Collects input from:The SC (the muscle and skin), Auditory, Visual, & Vestibular sys
Processes the information & Sends efferent output through the deep cerebellar nuclei
Which goes to the pyramidal & extrapyramidal sys.
These outputs are corrections/ adjustments of actual movements to bring them closer to the intended movements. This is done by modifying the movement and the muscle tone.
Located in the lateral hemispheres of the cerebellum.
Collects input from the cerebral cortex (controlling sensory and motor functions).
The output is directed back to the pre-motor area of the cerebral cortex with the information needed for specific movements of the extremities.
Cells & Their Connections
Cortex: Grey Matter (Outer Area)
Dendrites: Purkinje Dendrites & Golgi Dendrites
Axons: Climbing Axons & Granular Axons
Cells: Stellate Cells & Basket Cells
Purkinje cell layer
Cells: Purkinje Cells
Mossy Fiber Axons
Granular Cells: ~1/2 of
neurons in CNS 80,000
-200,000 parallel fibers
Axons connecting different areas and nuceli
Axons & Deep cerebellar nuclei
Contribution to Appropriate Movement
Series of cellular Interactions
Inhibits Purkinje cells
Inhibits Purkinje cells
Inhibits Granule cells
Excited by mossy fibers
Granule Cells: parallel fibers
Excited by mossy fibers
Excites Purkinje fibers
Purkinje Fibers: Sole output to all motor coordination
Excited by Climbing cells & multiple Granule cells
Inhibited by Stellate cells & Basket cells
The cerebellum also has the ability to memorize specific movements or a sequence of movements.
Memorization is done through repeated stimulations by climbing fibers on Purkinje cells.
Initially these movements or sequence of movements are carried out consciously, but after several repetitions the cerebellum has stored the information and can now unconsciously control the execution of these movements.
Since the cerebellum is constantly comparing the expected with the actual movements and making the appropriate adjustments, if there is cerebellar disease these corrections may not be carried out properly. As a result, the animals exhibit several typical clinical signs.
Vestibulocerebellum is compromised: balance
Wide-base gait Compensates unbalance
Cerebellar nystagmus Eyeball oscillation (failure to focus on a point)
Spinocerebellum is compromised: fine tuning movements
Hypotonia Lower peripheral muscle tone
Intention tremor Oscillating approach
Past pointing Exaggerated movement
Cerebrocerebellum is compromised: planned and memorized movements
Dysdiadochokinesia Sequencing problems
Dysarthria Vocal sequence problems
6. Limbic System & The Hypothalamus
Structures associated with the Limbic System
Translates input into emotions which are learned & committed to memory.
Physical connection, permitting neuronal communication between the two hemispheres
Connection between hypothalamus, mamillary bodies, thalamus, and cingulate cortex
Links specific memories with particular smells
Recognizes smell and associate them with specific memories
Filter background non-threatening odors
Connected to cerebral cortex & brainstem
Central relay of sensory and efferent information
the gustatory, auditory and visual systems
visceral and somatic information from the body
Regulates sleep and wakefulness
Involved in connections related to consciousness
Developments of long term memory
Spatial location memory
(first affected by Alzhimer’s disease)
Dentate gyrus (part of hippocampus)
Formation of memories
The sense of depression
Processing and memorizing emotions
Memory encoding and retrieval
Basal ganglia (not part of Limbic system)
Motor control and learning
Affected by Parkinson’s disease
Major Control for all limbic functions
Contains many specific nuclei (groups of neurons) that have one or more specific functions.
Maintains homeostatic conditions
Special role of the hypothalamus and its nuclei in maintaining homeostasis
Hypothalamic Connections: Processes sensory information and generates information for:
To the autonomic nervous system
Information travels via the brain stem and the reticular formation of the mesencephalon, it also goes through the pons and medulla oblongata.
To the diencephalon and cerebrum
Information travels principally via the frontal area of the thalamus.
To the hypophysis.
Information regulates the secretion of several hormones which control many vital functions of the body.
(Stimulation of GI activity)
Posterior Hypothalamic nucleus
Increased blood pressure
Lateral hypothalamic nucleus
Thirst and hunger
Medial preoptical nucleus
Decrease heart rate
Decreased blood pressure
Posterior preoptical and anterior hypothalamic nucleus
Water conservation (ADH)
Thermal sensory information comes from:
Internal febrile / pyretic receptors,
If the temperature of the circulating blood is elevated:
Preoptic Area: Activity is elevated
Efferent instructions for sweating and panting
instructions (through the autonomic nervous system) to
trigger vasodilation of peripheral capillary vessels for heat dissipation
Thirotropin (TRH) is inhibited (long term effect of a hot environment) to reduce metabolic activity and avoid excessive internal heat generation.
If the temperature of the circulating blood is low: (lower than the set point)
Preoptic Area: Activity is reduced
At the same time: all thermal information (from the preoptic area, sensory from the skin, and internal receptors) is integrated in the posterior hypothalamus.
To determine if the strategy to follow is to conserve or generate heat.
Cardiovascular activity is controlled by modifying arterial pressure and heart rate.
If blood pressure (arterial pressure) is high:
Preoptic Area: Activity is elevated
decrease Heart Rate
If blood pressure (arterial pressure) is low:
Posterior & Lateral Hypothalamic Nuclei: Activity is elevated
Increase Heart Rate
Efferent information is sent via cardiovascular centers,
Located in the reticular formation at the level of the pons and medulla oblongata, to the target tissues throughout the body.
Regulation of feeding activity
Two antagonistic centers regulate the actual feeding activity.
If the body is hungry (hunger center)
Lateral Hypothalamic nuclei: Activity is elevated
Increased food seeking behavior
If the body is not hungry (satiety center)
Ventromedial nuclei: Activity is elevated
Lack of an appetite
Both of these centers have the ability to detect a circulating concentration of key nutrients such as glucose to trigger initiation of feeding or cessation of feeding.
Bilateral damage to the lateral or ventromedial nucleus triggers an absolute lack of desire to eat or an insatiable appetite, respectively.
The result could be inanition leading to death or uncontrolled intake leading to obesity.
Two simultaneous mechanisms to control water content in the body.
If the electrolytes in the circulating fluids are detected to be too concentrated:
1- Water ingested & eliminated
Lateral hypothalamus (thirst center) : Activation increases
when there is water in the mouth & the lips are wet
This is temporary: lasts long enough for water to be absorbed GI
The animal will drink enough water to dilute circulating fluids.
2- Water conservation via urine volume reduction.
Supraoptical nuclei: Activation increases
Antidiuretic Hormone (ADH) / Vasopressin.
Increases water reabsorption in the collecting ducts of kidneys
Increases electrolyte elimination in the urine
Regulation of smooth muscle contractility
Related to several reproductive events
Produce oxytocin (hormone)
Stimulates contraction of myoepithelial cells (smooth muscles)
Found in the uterus & mammary glands
At birth the pressure of the fetus sends sensory afferent information to the hypothalamus which responds by secreting oxytocin.
Triggers contractile activity in the uterus to expel the fetus.
During lactation, stimulation of the mammary gland also triggers secretion of oxytocin,
Triggers contractile activity in the mammary gland to expel the milk in alveoli.
The stimulus can
be done manually by the young while suckling
(cleaning the mammary gland before milking)
& can also be
triggered by classical conditioning
(the cow hears the sound of the milking cans and starts producing oxytocin)
Hypothalamic neuroendocrine function.
Several of the hypothalamic nuclei have the ability to produce neurohormones
Stimulate or inhibit secretion of other hormones by the pars distalis of the hypophysis.
The trigger for the production of these hormones is the concentration of several compounds in circulation, which are detected as blood passes through the hypothalamus.