ANP 1106 - Final Exam

3 overlapping functions of the nervous system

1. sensory input

2. integration

3. motor output

sensory input

gathered information, monitor changes

Integration

To process and interpret sensory input and decide if action is needed

motor output

activates effector organs to cause a response

membrane ion channels

large proteins and different types of channels

leakage or non-gated channels

always open

gated channels

open or close in response to a stimulus

chemically gated

open with binding of a specific neurotransmitter

voltage gated

open and close in response to changes in membrane potential

mechanically gated

Open and close in response to physical deformation of receptors, as in sensory receptors

resting membrane potential

-70mV

generating a resting MP depends on

differences in K and Na concentration inside and out side cells

differences of permeability of the plasma membrane to these ions

graded potentials

incoming signals operating over short distances, strong

action potentials

long distance signals of axons

depolarization

-70mv to -65mv

hyperpolarization

-70mv to -75mv

magnitude varies with

stimulus strength

triggered by a stimulus in

neurons environment that opens gated ion channels

ap voltage gated ion channels occur in

muscle cells and axons of neurons

changes in voltage of

100mv

they no not decay over

distance

all ap are

alike and independant

CNS tells difference between a weak stimulus and a strong one by

frequency of impulses

aps occur only in

axons, not other cell areas

rate of propagation depends on

axon diameter and degree of myelination

continuous conduction

slow conduction that occurs in nonmyelinated axons

saltatory conduction

only occurs in myelinated axons and is about 30x faster

myelin sheaths

insulate and prevent leakage of charge

voltage gated Na channels are located at

myelin sheath gaps

group A nerve fibers

Large diameter, myelinated somatic sensory and motor fibers of skin, skeletal muscles, joints

Transmit at 150 m/s

group B nerve fibers

intermidate diameter, lightly mylienated fibres, trasnmit at 15 m/s

visceral sensory and motor fibers

group C nerve fibers

small and unmyelinated fibers

1mps

visceral sensory and motor fibers

synapse

A junction where information is transmitted from one neuron to the next.

neurons are functionally connected by

synapses, junctions that mediate information transfer

presynaptic neuron

conducts impulses toward the synapse

postsynaptic neuron

transmits impulses away from the synapse

axodendric synapse

axon to dendrite

axosomatic synapse

axon to cell body

axoaxonal

synapses between axons

dendrodendritic

dendrite to dendrite

somatodendritic

dendrite to cell body

electrical synapse

less common

chemical synapse

nerve impulse transmitted with assistance of a chemical neurotransmitter

synaptic cleft

the fluid-filled space at a synapse between neurons

neurotransmitters

Chemicals that transmit information from one neuron to another

Ach

acetylcholine

Ach is

released by all neurons that stimulate skeletal muscles and by many neurons of ANS

some Nt are and some are

excitatory and inhibitory

EPSPs

opening bc of NT cause simultaneously flow of Na and K in opposite directions

Na influx greater than K efflux

EPSPs trigger AP if EPSP is of threshold strength

IPSPs

opens chemically gated channels that allow entrance/exit of ions that cause hyperpolarization

makes post synaptic membrane more permeable to K or Cl

reduces post synaptic neurons to produce AP

if K channels open

it moves out of the cell

if Cl channels open

it moves into the cell

Post synaptic potential and their summation

one post synaptic neuron can receive inout from thousands of other new

it integrates these inputs at initial segment to detect weather it will fire an action potential

classification of NT by postsynaptic receptor structure

indirect vs direct

direct

binds directly to

opens ion channels

rapid responses

indirect

acts through intracellular second messengers

usually G protein pathways

broader larger longer lasting effects similar to hormones

NT receptors

channel - linked receptors - mediate fast synaptic transmission

G protein - coupled receptors - oversee slow synaptic responses

channel linked receptors cause

rapid synaptic transmission

G Protein-Linked Receptors

Responses are indirect, complex, slow, and often prolonged

Involves transmembrane protein complexes

Cause widespread metabolic changes

neuronal pools

functional groups of interconnected neurons

neuronal pools integrate

incoming information received from receptors of other pools

forward processing information to other destinations such as motor cortex to generate behavioural output

Patterns of Neural Processing: Serial Processing

Input travels along one pathway to a specific destination

all-or-none manner to produce specific, anticipated response

ex. spinal reflexes

reflexes

rapid automatic

occur over pathways called reflex arcs that have 5 components

what are the 5 components

receptor, sensory neuron, effector, CNS integration, motor neuron

a simple reflex arc

stimulus> receptor> sensory neuron>intermediate neuron> motor neuron>effector>response

Patterns of Neural Processing: Parallel Processing

Input travels along several pathways

Different parts of circuitry deal simultaneously with the information

One stimulus promotes numerous responses

Important for higher-level mental functioning

Example: A sensed smell may remind one of an odor and any associated experiences

Patterns of synaptic connections in neuronal pools called circuits

diverging, converging, reverberating, parallel

diverging circuit

One input, many outputs

An amplifying circuit

Example: A single neuron in the

brain can activate 100 or more motor

neurons in the spinal cord and

thousands of skeletal muscle fibers

converging circuit

Many inputs, one output

A concentrating circuit

Example: Different sensory stimuli

can all elicit the same memory

Parallel circuit

A circuit that contains more than one path for current flow.

may be involved in exacting mental processes such as mathematical calculations

reverberating circuit

signal travels through a chain of neurons, each feeding back to previous neurons

an oscillating circuit

controls rhythmic activity, sleep-wake cycle

Organization of the Somatosensory System

structurally organized; entered CNS, crosses midline at the brainstem or spinal cord, and then ascends to sensory cortex in parietal lobe

receptor level

sensory receptors respond to stimuli

sensation

ascending pathways occur in brain/awareness of stimulus

perception

interpreting information received from the senses

classification

type of stimulus they detect, thier body location, by thier structural complexity

mechanoreceptors

respond to touch, pressure, vibration, stretch, and itch

photoreceptors

respond to light

thermoreceptors

respond to changes in temperature

chemoreceptors

respond to chemicals

noireceptors

pain receptors

exteroreceptors

Sensory receptors that detect stimuli from outside the body, such as light/heat/pressure/chemicals.

interoreceptors

detect internal stimuli

proprioceptors

monitor the position and movement of skeletal muscles and joints

simple receptors

general senses, and may be unencapsulated or encapsulated dendritic endings

complex receptors

special sense organs (vision, hearing, equilibrium, smell, taste)

non encapsulated nerve endings

everywhere in the body, non myelinated, small diameter, respond fast to painful stimuli, temp changes, some to pressure

nerve endings that respond to cold are located

superficial dermis

heat ones are

deeper

A key player in detecting painful stimuli is a plasma membrane protein called

vanilloid receptor

epithelial tactile complexes

stratum basale of epidermis; light pressure

hair follicle receptors

free nerve endings that wrap around hair follicles

encapsulated nerve endings

one or more fiber terminals of sensory neurons enclosed in a connective tissue capsule

mechanoreceptors

Tactile corpuscles (Meissner's corpuscles)

phasic; small egg-shaped; just beneath the epidermis; light pressure, discriminative touch, vibration

numerous in sensitive skin and hairless skin like nipples, fingertips and soles of feet

lamellar corpuscle (Pacini corpuscle)

sensory receptor with a layered encapsulation found deep in the dermis that detects pressure on the skin surface

respond only when pressure is first applied

largest

bulbous corpuscles

found deep in dermis and hypodermis; detect deep continuous pressure

muscle spindles

receptors sensitive to change in length of the muscle and the rate of that change

tendon organs

proprioceptors in a tendon near its junction with a muscle

contraction

stretches tendon fibers - compression of nerve fibers - tendon organs - reflex contracting muscle to relax

joint kinesthetic receptor

A proprioceptive receptor located in a joint, stimulated by joint movement