Human Nervous System - EXAM 3

consists of around …..

a hundred billion neurons (nerve cells)

parts of the nervous system

• centeral nervous system (CNS)

• peripheral nervous system

parts of the central nervous system

brain and spinal cord

• the cranial of the central nervous system

part of the peripheral nervous system

spinal nerves

peripheral nervous system (PNS) info

• connect the CNS system to the sense organs

  • like organs for vision, hearing, smell, ant etc.

• responsible for the body funtion which are not under conscious control

  • heartbeat 

  • digestive system

The PNS is divided into…?

• sympathetic

• parasympathic

What is unique about the part of the PNS?

the two systems are opposing actions and check on each other to provide a balance

The nervous system uses…?

electrical impulse (travel along the length of the neuron

How fast are these impulses?

travel at up to 250 miles per hour

• unlike the endocrine system which takes many hours

human nervous system breakdown

main types neurons of peripheral nervous system

• sensory

• motor

sensory neurons

send message to the brain

motor neurons

deliver messages to glands and muscles

cell body

• largest part of neuron

• contains the nucleus and much of the cyptoplasm

• most of the metabolic activity of the cell

  • including ATP generation

  • synthesis of protein

cytoplasm 

area between the nucleus and the cell membrane

ATP

adenine triphosphate compound

• stores energy

dendrites

• short branch extensions spreading out from the cell body

• receive stimulus

• carry impulse from the environment or from other neuron and carry them toward the cell

action potentials

stimulus

axon

• a long fiber that carries impulses away from the cell body

• each neuron as ONE

• ends in axon terminals

axon terminals

a series of swellings

How many dendrites and axons on a neuron?

• hundreds of dendrites 

• usually ONE axon

myelin sheath

• a lipid layer that covers the axon of most neurons

• insulates and speeds up transmission of action potentials through the axon

Schwann cells

• produce the myelin 

• surround the axon

• in PNS

nodes of ranvier

gaps/nodes in the myeline sheath along the length of the axon 

functions of sensory neurons

• afferent

• carry impulses from the senses organs to the brain and spinal cord

• receptors detect external or internal changes and send information to the CNS in the from of impulses

functions of motor neurons

• efferent

• carry impulses from the brain and spinal cord to muscles or glands

• muscles and glands are 2 types of effectors

• in response to impulses, muscles ________ and glands secrete

contract; secrete

functions of interneuron

• connect sensory and motor neurons 

• carry impulses between them

• entirely within the CNS

dendrites

nucleus

cell body

myelin sheath

axon

node of ranvier

synapses

axon terminals

active transport

• creates a concentration gradient across the cell membrane for sodium ions (Na⁺) and potassium ions (K⁺)

• K⁺ ions are actively pumped INTO the cell while the Na⁺ ions are actively pumped OUT of the cell by the sodium-potassium pumps

• K⁺ diffuses out of the cell rather slowly but nonetheless faster than Na⁺ can diffuse in

diffusion process

• the unequal diffusion results in a net positive charge outside and excess of negative charge inside the membrane

a nerve cell has _____________ potential across its cell ____________ because of a _______ in the number of _______ and ________ charged ions on each side of the cell membrane

• electrical 

• membrane

• difference

• positively

• negatively

What is the electrical potential due to?

protein in the neurons knowen as sodium-postassium pumps that move sodium ions OUT of the cell and direct

What happens to the cytoplasm after active transport?

neurons contain more K⁺ ions and fewer Na⁺ ions than the surrounding medium

What does the cytoplasm also contain?

many negative charge protein molecules and ions

K⁺ ions can move out across the membrane _______ ______ than Na⁺ ions can enter in the cell

more easily

Do negatively charged protein molecules and ions move in and out of the cell?

NO; they do not move in and out of the cell

resting potential

charge difference of the leakage of positively charged ions out of the cell is a negative charge on the inside of the neuron’s cell membrane

the nueron is said to be ________ (_________ charged on the inside of the cell membrane and __________ charged on the outside). A nueron maintain this polarization until it is __________

• polarized

• negatively

• positively

• stimulated

stimulus

change in the environment that may be of sufficient strength to initiate an impulse

process diagram

diagram 1

diagram 2

sympathetic motor system

adrenergic system

parasympathetic motor system

cholinergic system

synaptic space

gaps between the neurons

• electrical signal has to jump across in order to continue

neurotransmitter

an electrical impulse is passed by a chemical signal called ____________