ASCI 229 Exam 2

neurologic functions

- sensory appreciation of tactile feeling
- detection of sound
- detection of pain

Nervous system is divided into 2 systems

Central Nervous System (CNS)
- brain and spinal cord

Peripheral Nervous System (PNS)
- nerves that emerge from the brain and spina cord and extend to muscles and glands

Nervous System Divided by: Direction of impulses

afferent
- nerve impulses travel toward the CNS (brain and spinal cord)
- sensory neurons

efferent
- impulses travel from CNS toward periphery
- motor neurons

Nervous System Divided: Functionally

autonomic
somatic

autonomic

activities taking place below the level of conscious perception

- not subject to voluntary control
- ex. pupil size, heart rate, body temperature regulation, blood glucose

somatic

voluntary motor activity

action potential (nerve signal)

the language of communication for neurons

neurons

nerve cells

neurological cells

- supporting cells
- glial cells
- make up most of the weight of nerve tissue
- do not transmit or receive nerve impulses
- give structural support and protection to neurons

2 types of neurological cels

astrocytes
oligodendrocytes

astrocytes

blood brain barrier
- send extensions of themselves to wrap around capillaries that are coursing through the neural tissue
- adds an extra barrier to the wall of these blood vessels so that substances in the blood cannot freely diffuse out into the brain tissue

Oligodendrocytes

send extensions of themselves to wrap around the axons of the neurons
- this extra covering creates an insulating layer called myelin

myelinated neuron anatomy

myelin sheath is made by oligodendrocytes in the brain and spinal cord, by Schwann cells in peripheral nerves

oligodendrocytes vs Schwann cells

the function of both cells = myelinate the axons of neurons

myelin sheath

myelin covering the axons facilitates faster impulse transmission by causing saltatory conduction along the nodes of Ranvier

white matter vs gray matter

gray matter = cell bodies
white matter = myelinated axons

somatic sensory function vs somatic motor function

somatic sensory: impulses sent to CNS from sensory receptors in muscles, skin, eyes, ears, and other sites that are consciously perceived by brain

somatic motor: conscious or voluntary initiation and control of movement and responses

neuron functions - rest vs firing

neurons at rest: not conducting an impulse
neurons are firing: generating an action potential

- neurons can both receive (through dendrites) and send (via axons) impulses

- determined by cell membrane activities

Resting state = resting potential

- nerve is not being stimulates to fire
- resting potential is negative = -70 mV inside the axon

depolarization

transient reversal of charge across neuron membrane (becomes positive) is created by flow of Na+ through membrane channels

Repolarization

change in cell's charge back to the polarized, negative resting potential

resting membrane potential

a state of stable imbalance across the cell membrane of a neuron at rest
- imbalance created by ions being pumped across the cell membrane, creating large concentration gradients
- molecular pump = Na-K ATPase membrane pumps

- pump 3 Na+ ions out of the cell while at the same time pumping 2K+ into cell

- net negative charge on inner aspect of the membrane = cell membrane is polarized

-70mv

resting membrane potential

- membrane pumps still active in maintaining negative charge

Na-K-ATPase

3 Na+ out of the cell, 2 K+ into the cell

Arrival of nerve impulse

causes a sequence of events at the cell membrane of the receiving neuron

sodium channels

open on the receiving neuron

sodium ions rush into cell

move down their concentration gradient

influx of Na+

depolarization

- causes positive charge (-70mV to 0)

potassium channels open when

sodium channels shut

- K+ moves out of the cell (negative value returns -70mV)

- Na+ outside, K+ inside

Pumps and channels

only Na+ flows through Na+ channels and same for K+

- channels are not open at the same time

threshold voltage

-55 mV, all the channels snap open and permit a dramatic influence of more Na+

if depolarization does not reach -55 mV at the axon hillcock

an action potential will not result

all or nothing principle

if the signal received at the dendrites is weak, no action potential will result at all

synapse

how an impulse travels from nerve to nerve or some other target

Neurotransmitters

Chemicals that transmit information from one neuron to another

excitatory vs. inhibitory neurotransmitters

excitatory
- cause Na+ influx and change in membrane voltage toward threshold

ex. acetylcholine

inhibitory

- hyperpolarize cell, making membrane potential more negative and moving away from threshold

ex. glycine, GABA

be able to label a neuron

slide 42

central nervous system: brain

cerebrum
diencephalon
cerebellum
brain stem - midbrain, pons, medulla oblongata


- know locations

cerebrum

Largest part of the brain; responsible for voluntary muscular activity, vision, speech, taste, hearing, thought, and memory.

diencephalon

thalamus, hypothalamus, pituitary

- sensory and autonomic function

cerebellum

little brain

- integrates visual, auditory, and equilibrium input to maintain balance
- coordinates and smooths movement initiated by motor cortex

midbrain

motor movement, particularly movements of the eye, and in auditory and visual processing

pons

unconscious processing - sleep, breathing

medulla oblongata

Part of the brainstem that controls vital life-sustaining functions such as heartbeat, breathing, blood pressure, and digestion.

lobes of the cerebrum

frontal, parietal, temporal, occipital

gyri

folds of the brain

sulci

grooves of the brain

frontal lobe

- cognition
- reasoning
- higher language, poetry, music
- motor cortex = voluntary movement

parietal lobe

- sensory tactile information
- pressure
- touch
- pain
- anterior-most gyrus in the parietal lobe is the somatosensory cortex

occipital lobe

visual processing

temporal lobe

auditory and memory encoding

spinal cord divisions

cervical, thoracic, lumbar, sacral

nerve = bundle of neurons

a nerve contains multiple fascicles of neurons

Protective Layers of the CNS

brain and spinal cord encased in bone
- covered in 3 adherent membranes = meninges
- float in cerebrospinal fluid
- blood brain barrier - includes astrocytes (block substances in blood from diffusing into brain)

Meninges

pia mater, arachnoid mater, dura mater

pia mater

Innermost layer, thin, transparent, tightly adherent to brain surface contours

arachnoid

middle layer
vascular
weblike
- cerebrospinal fluid = subarachnoid space

dura mater

outermost layer, thicker, nonexpansile

spinal tap

placement of a needle through an intervertebral space into the subarachnoid space to withdraw CSF
- should look like tap water

- fluid analyzed for glucose, protein, cells

meningitis

swelling arises from within, bony encasement becomes lethal

- inflammation and hemorrhage in arachnoid

Peripheal nerves

spinal nerves exit the spinal cord at each intervertebral junction and extend to the tissue in that body plane of region

cranial nerves

12 pairs
- the ventral aspect of the brain but are part of the peripheral nervous system

vagus neve (X)

has a role in nearly all visceral functions = parasympathetic

automatic nervous system: sympathetic vs parasympathetic

sympathetic: flight or flight

parasympathetic: rest and digest

sympathetic nervous system

- nerves emerge from spinal cord in the thoracolumbar segments

- preganglionic neuron is short, postganglionic neuron to target organ is long

parasympathetic nervous system

- nerves emerge from craniosacral segments
- nerves coming out of the brainstem and spinal cord

- preganglionic neuron is long, postganglionic neuron to target neuron is short

somatic vs autonomic efferents

somatic = one long neuron from spinal cord to muscle

autonomic = are broken by a synapse at a ganglion

sensory functions

specialized sensors in the periphery of the body that react to specific stimuli which generates a nerve impulse that afferent fibers conduct to the central nervous system

- interpreted by brain as a type of sensation

general senses

visceral sensation, temperature, nociception (pain), touch, pressure, vibration, proprioception (position)

special senses

olfaction, vision, gustation, equilibrium, hearing

eyeball - 3 layers outer to inner

- sclera (fibrous layer)
- choroid (vascular layer)
- retina (nervous layer)

sclera

outer layer - fibrous
- cornea

chloroid (uveal layer)

middle layer - vascular
- ciliary body
- iris
- tapetum
- contains pigments, smooth muscle, and blood vessels

retina

inner layer - nervous

tapetum

A reflective layer of the choroid in the eyes of many animals, causing them to shine in the dark.

- humans/swine do not have them

aqueous humor

fluid in the eye, found between the cornea and the lens

- flows from posterior chamber to anterior chamber, then drains out

**** know how to trace the pathway of aqueous humor synthesis and flow

photoreceptors

light has to traverse all layers of the retina before encountering the actual photoreceptors

opthalmoscopy

posterior aspect of the eye = fundus
- fundic exam
- fundic blood vessels are unique to each organism

glaucoma

high intraocular pressure

- caused by impaired outflow in drainage canals of Schlemm
- fluid increases and puts pressure on cornea and retina

results:
- pain
- blindness
- corneal edema (fluid build up)

tonometer

instrument used to measure intraocular pressure

cataract

thickening and opacity of the lens

eyelid

lacrimal puncta, meibomian glands, lacrimal apparatus

- exist to make and disperse the tear film over the corneal surface, then drain it appropriately

external ear

pinna (ear lobe), external canal, tympanic membrane

middle ear

ossicles, eustachian tube

inner ear

cochlea (hearing)
semicircular canals (balance)

cochlea

a coiled, bony, fluid-filled tube in the inner ear through which sound waves trigger nerve impulses

semicircular canals

position sense and balance
- contain vestibular apparatus

vestibular apparatus

3 canals lie in a slightly different plane to detect head movement in different directions

- causes action potentials to be sent up to the brain up the vestibular division of the CN VII

- tells brain what positive the head is in, relative to the horizon = balance

otoscopic exam

evaluates for ottis externa
ear drum problems
foreign bodies
can be very painful for patient

organ of corti

an organ in which vibrations transmitted to fluid in a closed tube causes fluctuations of the basilar membrane and causes hair cells to bend against the tectorial membrane

- sends impulses to auditory nerve of the brain

what signs might you see in an animal with a clogged nasolacrimal duct

infection
tears building up
redness
vision blurred
swelling

**** know the effects of sympathetic and parasympathetic on targets of body chart in neurology worksheet

Functions of Bones

support
protection
leverage
storage
hematopoiesis

hematopoiesis

blood cell formation

characteristics of bone

connective tissue, sparce cells embedded in a hard matrix

osteoblasts

secrete the matrix, which is composed of collagen fibers embedded in a gelatinous substance containing protein and polysaccharides

cause the matrix to ossify by means of hydroxyapatite crystals: calcium and phosphate

osteocytes

hydroxyapatite hardens and crystallizes - become sequestered in tiny spaces called lacunae

canaliculi

channels that allow for communication via other bone cells and the outside world

osteoclasts

eat away at bone to remodel it and to release the stored calcium back into the bloodstream in times when the animal is low in calcium

- how skeleton serves as storage for calcium