BI 121 Exam 4 GRCC (Forbes)

Sensory

Receive stimuli from environment via sensory receptors in PNS ex: sound

Integration

CNS processes all sensory signals and creates sensations, memory, thoughts, and actions

Motor

CNS sends impulse to stimulate movement in effectors outside of the nervous system. Ex: muscles, glands

neurons

produce transmit, and interpret nervous impulses

neuralgia

supportive cells around neuron. nourish insulate and structural support- make new neuralgia our whole lives

synapses

gaps in adjoining neurons

neurotransmitters

chemicals that carry stimulus across synapses

CNS

brain and spinal cord

PNS

cranial and spinal nerves

Afferent neurons

sensory neurons bring stimulus towards CNS

Efferent Neurons

motor neurons bring stimulus away from CNS to PNS

PNS divisions

Sensory and Motor

Motor Divisions of PNS

Somatic, and Autonomic

Autonomic nervous system

sympathetic and Parasympathetic

Sympathetic nervous system

away from homeostasis

Parasympathetic nervous system

back to homeostasis

myelin sheath

insulative layers of membrane of neuroglial cells. called schwann cells in PNS

MS

autoimmune disorder, possibly virus caused. Inflames and destroys myelin sheath in CNS reducing and stopping nervous impulses as hard scars are formed on the axon.

ALS amyotrophic lateral sclerosis

progressive degenerative disease that affects motor neurons in CNS/PNS. Motor neurons dies, control of skeletal muscles is lost. Cause unknown and no cure.

astrocytes

tissue structure, ion regulation, glucose metabolism, growth factor, directs nutrients to neurons, reinforce blood-brain barrier. work with neurons for learning and memory.

the blood/brain barrier

tight capillaries overlapping tight membrane junctions without clefts. no free movement of chemicals into brain tissues.

olgiodendrite

mylein in CNS. can join adjacent neurons providing structural framework, secrete nerve growth factor for neuron repair.

microglial cells

motile, phagocytize bacteria, and debris.

ependyma

lines cavities of CNS, regulate composition of CSF and ciliated cells help circulate CSF.

path note: most brain tumors and cancers are

composed of neurogila

regeneration of PNS axons

damage to cell body kills cell. damage to axon is repairable.

axons cannot regenerate segments..

greater than 3mm

step 1 in PNS axon regeneration

distal to injury axon and myelin degeneration and fragment.

step 2 in PNS axon regeneration

proliferation of schwann cell. macrophages move into the area and remove debris distal to site of injury.

step 3 in PNS axon regeneration

axon elongates and grows into proliferation path of schwann cell

step 4 in PNS axon regeneration

as axon elongates into path, schwann cell wraps around. normal function will be regained in axon reestablishes its normal synaptic contacts.

Neuroma

painful nerve mass. tangled mass of axons. problem in amputations.

CNS axons cannnot be repaired why?

oligodendrites will not reproduce, which produce the mylein. Astrocytes produce scar tissue at injury site.

Leak non-gated channels

selectively permeable channels that are always open.

What is responsible for the TMP

leak gated channels

chemically gated channels

open when bound to chemical ex: ACH

what is responsible for maintaining synaptic potentials?

chemically gated channels

voltage gated channels

open in response to change in trans-membrane potentials ex: NA, K, Ca ions

mechanically gated channel

response in distortion of dermis

Trans-membrane potential

the amount of electrical charge difference between 2 sides of a membrane when the neuron is at rest (-70mv)

K+

major integral ion

Na+

major external ion

ion distance is determine by?

selective ion leak channels, and pumps.

excitable cells

cells that can produce electrical signal

resting potential

The TMP -70mv, of a neuron at rest. regulated by leak channels.

Graded potential

a decreased in TMP with distance from the stimulus. regulated by chemically gated channels.

local current

movement of positive ions parrel to the membrane. Internal ions Na+ move into cell, move along the inner surface of membrane. spread in both directions.

Action Potential

changes in TMP. transmitted via propagation along the axon.

An action potential begins with?

chemically gated Na+ channels.

an action potential propagates via

voltage gated channels.

action potentials propagate along the axon via

continuous prorogation

continuous prorogation

un-myleinated axons. series of local current membrane depolarizations propagate the action potential down the action membrane.

saltatory progation

occurs in myelinated axons. ions cannot flow through myelin so ions cross at nodes.

synapse transmission

action potentials must be transmitted across the synapse to the next neuron.

chemical synapses

rely on neurotransmitters. ca+ into the s. knob. Ach via exocytosis. Ach binds to receptor opening chemically gated channels. producing a graded depolarization. Ach is broken down by enzyme and choline is reabsorbed into knob to make new ach.

electrical synapses

rely upon direct transmission of electrical impulse from one neuron to another via physical contact of the membranes via gap junctions.

convergence

multiple neurons communicate message to single neuron. PNS to CNS. afferent sensory impulses.

divergence

single neuron communicates message to multiple neurons. CNS to PNS. Motor efferent impulses.

serial

neurons arrange in linear fashion.

Neurotransmitters regulation

-enzymes can break NT down

- neuro-modulator: block NT action or alter release ex: endorphin

- recycle: synaptic knob reabsorbs ACH.

endrophins and enkephalins bind to opiate pain receptors in brain and block ?

substance P ( a NT which transmits pain)

opiate addicts have withdrawal pains why?

body has stopped producing own endorphins in presence of opiates. No defense against pain during withdrawals.

antagonist

block NT action, binds to receptor site.

agonist

aids NT, activates a receptor ex: smoking: nicotine and dopamine.

CNS divisons

1. Spinal cord

2. Brain

3. Cerebrum

4. Cerebellum

5. Diencephalon

6. Brainstem

meninges cover

cover all divisions of CNS

Dura mater

vascular CT with nerves and forms internal periosteum of skull bones and covers spinal cord as it passes through vertebrae.

epidural space

space between vertebrae and dura mater

subdural hematoma

trauma to head may cause blood to collect in space below dura matter

arachnoid mater

avascular membrane that reabsorbs CSF.

Dural Sinus

blood flows in space between outer and inner layers of dura mater.

Pia mater

membrane covering the brain. Vascular with nerves. Nourishes CNS cells with CSF secretion and attaches dura mater to spinal cord.

subarachnoid space

seperates arachnoid and pia mater CSf is re absorbed

CSF

similar in compostion to plasma from which it is derived.

functions of CSF (4)

cushions, nourishes CNS. Transports wastes to blood. Ion Balance.

choroid plexuses

capillary bundles that secrete CSF into ventricles

meningitis

viral or bacterial inflammation and infection of meninges. affects vision, hearing, IQ, and may result in death.

Hydrocephalus

results when CSF production is greater than absorption due to infection, clot, or tumor.

conus medullaris

end of spinal cord- L1 and L2

cauda equina

nerves radiating from inferior lumbar enlargement.

central canal

continuous with brain ventricles

gray matter

cell bodies, neuroglia, unmyelinated axons.

white matter

myelinated axons arranged in tracts.

nerve tracts

axons with common origin, teminus, and function. Cross over in cord and brain stem.

ascending tracts

sensory affector impulses.

descending tracts

carry motor efferent impulse down to neurons

damage to a tract anywhere along its length will ?

affect its funciton

damage to descending tract

loss of motor functions inferior to damaged area.

damage to ascending tract

loss of sensation function inferior to damaged area.

Protein Blockers

block CNS protein that prevents axon regeneration

PNS Neuron Transport

PNS neuron + growth factor

Neural Stem Cell

brain stem cells induced to form patches.

functions of spinal cord

spinal reflex arc transmission

conduit for impulses to afferent and from efferent brain

reflex arc

pathways for impulses reflexes that do not go through brain, ex: heart rate, blood pressure, sneezing, knee jerk.

reflex arch cycle

1. receptor receives stimulus

2. sensory neurons deliver

3. inter-neurons- CNS neurons relay stimuli. not always present.

4. motor neuron pass stimulus to effectors.

5. effector- turn stimulus into action. ex: muscle contraction.

functions of the brain

process sensory information, memory, reasoning, coordination of muscles, visceral activity, personality.

Convolutions

increase surface area of gray matter

cerebral cortex

outermost layer of gray matter in cerebrum . contains cell bodies.

white matter of cerebrum

inner most layer of cerebrum that contains myleinated axons.

motor functional lobe

frontal lobe