ch 10, 12, 13, HW, Case Studies

what are the spinal cord functions?

process reflex, integrate EPSPs and IPSPs, conduct sensory impulses to the brain, and motor impulses to effectors.

what is the spinal cord protected by?

bone (vertebrae), connective tissue (meninges), and cerebrospinal fluid

what are the 3 layers of the meninges?

dura mater, arachnoid mater, pia mater

The spinal cord begins as an extension of the _________ at the level of the _________ and terminates at ___________.

medulla oblongata; foramen magnum; the level of L2.

where does incoming sensory info enter?

through the posterior cord.

how is incoming sensory info transmitted to the brain?

through ascending fibers and then the brain integrates/interprets the info

how does outgoing “motor” info descend?

through the anterior cord.

what do spinal nerves connect?

CNS to sensory receptors, muscles, and glands.

what system are spinal nerves a part of?

peripheral nervous system.

how many pairs of spinal nerves?

31, mostly corresponding to the levels of vertebra

what is a spinal nerve attached to and how?

a segment of the spinal cord by anterior and posterior roots

what do spinal nerves enter/exit through?

intervertebral foramen.

what are dermatomes?

segments of skin containing spinal nerves.

what do dermatomes do?

carry somatic sensory nerve impulses to the brain.

what is the cervical plexus?

network of nerves in the skin and muscles of the head, neck, diaphragm, superior portion of the shoulders, and chest.

what is the brachial plexus?

nerve supply to the shoulders and upper limbs

what is the lumbar plexus?

nerve supply of skin and musculature of lower limbs

what is the sacral plexus?

motor and sensory nerve supply for the posterior thigh, most of the lower leg, the entire foot, and part of the pelvis.

how does the spinal cord contribute to homeostasis?

by propagating nerve impulses and integrating information

how does information travel in the spinal cord?

white matter tracts conduct nerve impulses to and from the brain, while gray matter receives and integrates incoming and outgoing information to perform spinal reflexes.

what is a reflex?

a fast, involuntary, unplanned response to a particular stimulus

what is ipsilateral?

same side

what is contralateral?

opposite side

what is monosynaptic?

one

what is polysynaptic?

more than one

what is reciprocal innervation?

neural circuit simultaneously contracts one muscle and relaxes its antagonists

what does a stretch reflex do?

causes the contraction of a muscle that has been stretched.

what does a tendon reflex do?

causes the relaxation of the muscle attached to the stimulated tendon.

what does a flexor (withdrawal) reflex do?

causes withdrawal of a limb to avoid injury or pain.

what does a crossed-extensor reflex do?

maintains balance during a withdrawal reflex.

what are the traumatic injuries?

monoplegia, paraplegia, hemiplegia, quadriplegia.

what does the damage that results from traumatic injuries depend on?

the degree of spinal cord section or degree of compression of the segments involved.

what does the extent of paralysis from traumatic injury depend on

location of the injury:

A – no function from the neck down

B – some arm and chest muscle control

C – most thigh muscles

D – most leg muscles

what are shingles

Acute infection of the PNS caused by herpes zoster virus (also causes chickenpox). causes pain, discoloration of the skin, and line of skin blisters.

what are some disorders?

spinal cord compression, degenerative diseases (multiple sclerosis, amyotrophic lateral sclerosis), and poliomyelitis (polio).

somatic and special senses (esp. _______) = sensory input to CNS

cranial nerves

functions of nervous system?

sensory input, integrative (brain), motor output (effectors)

which function:

detects changes through sensory receptors

sensory input

digestive system can _____ independently of nervous system input

"act"

CNS to motor output = somatic nervous system (_____(1)_____) and autonomic nervous system (_____(2)____)

(1) voluntary

(2) involuntary

which function:

analyze incoming sensory info, store some aspects, make decisions regarding appropriate behaviors

integrative (brain)

which function:

respond to stimuli via effectors

motor output

examples of motor output (effectors)?

muscles and glands

nerve impulse is called an?

action potential

action potential:

due to movement of?

ions across cell membranes

action potential: due to movement of ions across cell membrane; esp. what ions?

sodium and potassium

receives communication from adjacent neurons =

dendrite

"supports" neurons =

neurological cell

DNA, protein synthesis, etc. =

cell body

transmits action potentail =

axon

allows for integration of a great deal of info from other neurons

multipolar neuron

multipolar neuron:

possesses a single ___(1)___ and many ___(2)___

(1) axon

(2) dendrites

has 2 distinct structures extending from the cell body - an axon and dendrite - uncommon - esp. special senses

bipolar neurone

only occurs as a general sensory neuron

pseudo-unipolar neuron

neurons can be classified based on?

the direction of nerve impulse propagation

conveys info to the CNS =

sensory/afferent neurons

conveys action potential to the CNS =

motor/efferent neurons

process sensory info and elicit motor response =

interneurons/association neurons

interneuron =

usually multipolar axon

"nerve glue", provides lattice-work, maintains proper ionic environment, etc. =

neuroglia

are neuroglia electrically excitable?

NO

neuroglia make up about ________ the volume of the nervous system.

half

what can neuroglia do?

multiply and divide

can neurons multiply?

NO

there are 6 kinds of neuroglia, specifically:

4 in CNS, 2 in PNS

the myelin sheath is produced by ___(1)___ (PNS) and ___(2)___ (CNS) and it surrounds the axons of most neurons.

(1) Schwann cells

(2) oligodendrocytes

allow communication over short and long distances

action potentials (AP)

allow communication over short distances only

graded potentials (GP)

production of an AP or a GP depends on the existence of?

resting membrane potential and certain ion channels

in the brain:

the _________ directs the sensory info to the appropriate lobe

thalamus

the ________ interprets info and sends a response

brain

sensory impulses ascend up the ___(1)___ to the ___(2)___

(1) spinal cord

(2) brain

motor impulses descent down the spinal cord to an ________, which responds

effector

- ___(1)___ channels respond to chemical stimuli

- ___(2)___ binds to the receptor

- a.k.a. chemically gated

- i.e. ___(3)___

(1) ligand-gated

(2) ligand

(3) a drug

- ___(1)___ channels responde to mechanical vibration or pressure stimuli

- i.e. ___(2)___

(1) mechanically-gated

(2) in skin

___(1)___ channels respond to direct changes in membrane potential

voltage-gated

gated channels that open in response to binding of ligand (chemical) stimulus

ligand-gated channels

gated channels that open in response to mechanical stimulus (like touch, pressure, vibration, tissue stretching)

mechanically gated channels

gated channels that open in response to voltage stimulus (change in membrane potential)

voltage-gated channels

the membrane of a non-conducting [resting] neuron is relatively positive outside and negative inside; this is determined by...?

- unequal distribution of ions across the plasma membrane and selective permeability of the neuron's membrane to Na and K

- most anions cant leave the cell

- Na/K ATPase pumps 3Na+ out in exchange for 2K+ in

stimulus strength =

amplitude of graded potentials depends on the stimulus strength

graded potentials: stimulus strength

Remember: an action potential is not generated until __________ is reached [usually ~55mV]

"threshold potential"

summation =

graded potentials can be added to become larger in amplitude

action potentials have 2 phases:

depolarization, repolarization

depolarization =

becoming more positive inside

repolarization =

returning to more negative inside, requires energy Na/K ATPase

action potentials can only occur if the membrane potentials reaches...?

threshold

action potentials are "all or none" - i.e. ___________

either a neuron "fires" or it does not

Action Potentials: the Status of Na+ and K+ Voltage-Gated Channels

when:

- all voltage-gated Na+ and K+ channels are closed

resting state

Action Potentials: the Status of Na+ and K+ Voltage-Gated Channels

when:

- membrane potential of axon reaches threshold - the Na+ channel activation gates open

- Na+ rushes in

depolarizing phase

Action Potentials: the Status of Na+ and K+ Voltage-Gated Channels

when:

- Na channels inactivation gates close and K channels open

- K+ leaves neuron

- inside becoming negative again

repolarizing phase begins

Action Potentials: the Status of Na+ and K+ Voltage-Gated Channels

when:

- K+ outflow continues

- as more K ions leave the neuron, more negative changes build up along inside surface of membrane

- K+ continues leaving neuron

- inside becoming negative again

repolarization phase continues

in order for communication to occur from one body to another, action potentials must travel from where they arise at the trigger zone to the axon terminals - this traveling is called?

propagation

action potentials do not die out; they keep their strength as they spread across the membrane of a neuron - remember:

all or nothing principle

factors that affect propagation speed:

- axon diameter

- amount of myelination

- temp

amount of myelination =

myelin increases speed of AP propagation

junction between neurons or between neuron and an effector

synapse

gap junctions connect cells and allow the transfer of info to synchronize the activity of a group of cells

electrical synapse

electrical synapse:

ensures that all cells fire ____(1)____ at about the same time - ions flow directly between cells - i.e. ____(2)____

(1) action potentials

(2) between cardiac muscle cells

one way transfer of info from a presynaptic neuron to a postsynaptic neuron

chemical synapse