module 4 Flashcards
gray matter vs white matter
gray matter: contains nerve cells and their processes
white matter: contains nerve fibers that connect the brain with the spinal nerves
cranial nerves and their function
- emerge from brain stem
- cranial nerves do not have dorsal or ventral roots
- afferent sensory nerves (optic)
-efferent motor nerves (hypglossal)
-mixed cranial nerves (vagus)
spinal cord anatomy
-continuations of the medulla oblongata
-divided into segments each with a pair of spinal nerves
- in all species the first spinal nerve emerges from the vertebral column at the joint between the skull and the first cervical vertebra
spinal cord tract
-bundle of fibers within CNS is called a tract
-spinal cord tract provides routes for conduction of information to and away from the brain
Cerebellum
- coordinates movement, smoothness of actions, and maintenance of equilibrium (hand-eye coordination)
-is damages, the eyes can follow an object but animal cant pick it up
hindbrain
contains brainstem
brainstem
pons: regulates breathing activity
medulla oblongata: contains centers that control several autonomic functions (cardiovascular activity, swallowing, vomiting, digestion
midbrain: mesencephalon
forebrain
contains cerebral cortex, basal ganglia, thalamus, and hypothalamus
cerebral cortex
forebrain telecephalon
- complex control center with somatosensory and higher motor functions
- motor portion response to sensory stimuli by sending commands to skeletal muscle (catching or copulation)
- somatosensory functions include receiving and integrating touch, temperature, pain, and pressure sensations
basal ganglia
forebrain telecephalon
important for motor coordination; a switch center for impulses from motor system
types of papillae (taste buds)
foliate: moderate numbers on tongue
located on tongues lateral surface and flat anterior surface
fungiform: moderate numbers on tongue
located on tongues lateral surface and flat anterior surface
circumvallate: most numerous papillae that contain taste buds
found on posterior (base) surface of the tongue in the shape of a v
hypothalamus
forebrain diencephalon
important for homeostasis
contains releasing hormones that influence the anterior pituitary
synthesizes oxytocin and ADH, which are stored in the posterior pituitary
contains centers for regulation of body temp, thirst, and hunger
plays a role in sexual response and mating behaviors
eustachian tube
equalizes pressure between atmosphere and middle ear
thalamus
forebrain diencephalon
major relay center for sensory information on its way to the cerebellum
attenuation reflex
reduces intensity of low-frequency sound in order to mask them as background noise
{protects cochlea} from high frequency vibrations
involves contraction of stapedius muscle and tensor tympani muscle
muscles contact, movement of ossicles is dampened and sensitivity of acoustic apparatus decreases
middle ear
cavity filled with are, containing three small, conected bones referred to as ossicles (malleus, incus, and stapes) or (hammer, anvil and stirrup)
inner ear
contains the cochlear and vestibular systems
contains saccule that is integrative in both systems
cochlear vs vestibular system
cochlea: receives and transmits sounds and vibrations
vestibular: detects changes in head position and movement
outer ear
consists of external pinna (auricle) and external (auditory) ear canal (acoustic meatus)
cochlea
complex coiled organ of inner ear that is filled with fluid
the three canals of the cochlea
scala media (cochlear duct): filled with endolymph fluid
scala tympani (below scala media separated by basilar membrane): filled with perilymph fluid
scala vestibuli (above scala media): contains perilymph fluid
fundic exam
examination of retina
atropine used (pupil dilation)
tympanic membrane
acts as separation between outer and middle ear, contains glands that secrete cerumen
flourescein dye test
evaluate integrity of cornea
o Flourascein paper strips with sterile solution applied
o Normal cornea does not pick up dye
o If cornea is damaged, the flourascein will enter and appear green (corneal ulcar, common in small animals and horses
schirmer tear test
commonly used to evaluate basal tear production
Decrease tear production can cause ocular infections and corneal ulcers
tear production
- Lacrimal gland present on the dorsolateral surface of each eye drains secretions (tears) onto the eye
- Tears empty into puncta, which eventually drain into the nasolacrimal ducts and empty into nostrils
three layers of the eye
- Outer to inner (fibrous layer, vascular layer (uvea), nervous layer)
- Fibrous: comprised of opaque, dense sclera and the circular transparent cornea
- Vascular: consists of choroid, ciliary body, and iris
o Location of tapetum lucidum, on dorsal portion of choroid
o Specialized layer that reflect light - Nervous: consists of the retina and associated nerves and blood vessels
consensual pupillary reflex
- When one pupil reflexively reacts (ex: light), the other also reacts
pupillary light reflex
o Light directed into the eye causes constriction of the pupil (pupil constriction under the influence of PNS, part of the ANS)
o Absence of light causes pupils to expand to allow more light in
side effects of atropine on eye
- Atropine in the eye causes muscles to relax and the pupil to dilate
- Counteracts the effect of acetylcholine which is the NT of the parasympathetic NS, and causes constriction of pupil
stretch receptors/stretch reflex
Patellar reflex/knee jerk reflex
Stretch reflexes are useful in localizing pathological conditions that cause interruption or damage of a peripheral nerve
myelinated nerves vs non-myelinated
o Nerve transmission is much faster in myelinated axons
o Myelin protects, insulates, and assists with axon nerve transmission
action potential definition and process
An action potential (AP) is depolarization followed by repolarization
Propagation of action potentials along the length of a neuron is the mechanism for nerve signal transmission
After AP, sodium-potassium pumps in the membrane, pump sodium out of the cell and bring potassium into the cell which restores resting distribution of sodium and potassium ions, allowing membrane to recover and prepare for another AP
voluntary activities
skeletal muscle
involuntary activities
- Heart rate
- Contraction of blood vessels
- Ejaculation
- Saliva secretion
- Release of glucose from liver
dendrites
receives impulses for the neuron
axons
transmits signal to adjacent cells
excitatory neurotransmitters
Excitatory NT allows sodium to enter and potassium to leave the cell resulting in a more positive interior (hypopolarization)
* Makes it easier to generate an action potential
inhibitory neurotransmitters
Inhibitory NT allows potassium to leave or chloride to enter the cell resulting in a more negative icf (hyperpolarization)
* Making it more difficult to generate an action potential
hyperpolarization
occurs when an inhibitory neurotransmitter (serotonin, GABA) is released, it causes some potassium channels to open, and potassium rushes out of the cell
* This causes ICF more negative than before, and it is more difficult for depolarization to occur
hypopolarization
when excitatory neurotransmitter is released
RMP
Resting Membrane Potential (RMP) value describes the transmembrane voltage of an inactive cell
* A neuron RMP is -70mV due to the presence of Na+ in a higher concentration outside the cell
* Therefore, ICF has negative charge
depolarization
caused by stimulation that increases membrane permeability to sodium (positively charged ion enters cell and changes charge polarization between ecf and Icf
repolarization
occurs immediately after a membrane depolarizes
* Positively charged ions rush outside the cell, bringing the cell RMP back to negative
neuron
Neuron (nerve cell) is the functional unit of the nervous system
synapse
Synapse is the junction between two neurons
sympathetic NS
Origins in the thoracolumbar part of spinal cord
Also called adrenergic system, because the main neurotransmitter released at effector organ is adrenaline (epinephrine)
Signals sent from hypothalamus and brain stem (medulla and pons) through the spinal cord to the sympathetic chain ganglia
* Sympathetic ganglia only short distance from the spinal cord
* Postganglionic fibers are long and send signals from ganglia to effector organs
o Norepinephrine is the neurotransmitter
* Adrenal medulla cells are postganglionic neurons
* Adrenal medulla secretes large amounts of norepinephrine and epinephrine directly into the blood when stimulated by acetylcholine from sympathetic preganglionic neurons
* Causes massive generalized systemic effect (fight or flight) in emergency situations
sympathetic NS effects of ANS
- Decrease gastrointestinal motility and secretion
- Increase heart rate
- Increase force of heart contraction
- Effect on blood vessel constriction and dilation
- Increases basal metabolism
- Dilation of pupil size
parasympathetic NS
Origins in the sacral part of the spinal cord and cranial nerves
Also called cholinergic system because acetylcholine is the main neurotransmitter
Signals arise in the hypothalamus and brainstem and pass through certain cranial nerves
* Most pass though vagus nerve (X or tenth nerve) via postganglionic fibers at effector organs
parasympathetic effects on ANS
- Increase gastrointestinal motility and secretion
- Decrease heart rate
- Decrease force of heart contraction
- No effect on blood vessel constriction and dilation
- No effect on basal metabolism
- Constriction in pupil size
motor/efferent division
division of PNS, controls involuntary unconscious body function through effector organs (cardiac muscle, smooth muscle, exocrine glands)
sensory/afferent division
division of PNS part of the cranial nerves (optic nerve, primary taste nerves)
* Afferent axons project from olfactory cells
PNS
- Peripheral nervous system (PNS)
o Makeup and function
All nerves and ganglions outside of CNS (spinal nerves, cranial nerves, nerves of autonomic nervous system)
Divided into somatic (sensory +motor neurons) and autonomic (only motor neurons)
Somatic (involuntary) sensory neurons bring info to CNS and CNS initiates commands carried out by motor neurons.
Autonomic (involuntary) – controls heart rate and other internal organ activity like blood pressure, body temp, and digestion.
CNS
- Central nervous system (CNS)
o Makeup and function
brain and spinal cord – processes sensory information from PNS and initiates commands
Nervous system key functions
o Main function is to control and regulate activities of the body
o Helps body adjust to changes in the environment (internal or external)
NS works together with the endocrine system to do this regulation
NS uses nerves/neurotransmitter substances, Endo uses hormones
