Ch. 19 - The Nervous System

parts of the nervous system

• central nervous system

• peripheral nervous system

what does the central nervous system consist of?

• brain

• spinal cord

function of the CNS

receives info from body, processes it, decides on course of action, sends messages to different parts of the body to carry out an action

function of the spinal cord

contains nerve cells (neurons) which transmit info between the brain and the PNS

function of the brain

processes info, decides on a course of action, and sends messages bcak out to the PNS via the spinal cord

what does the PNS consist of?

a vast network of nerve fibres and cell bodies outside the CNS

the brain is protected by

strong skull or cranium

meninges

membrane for protection - the brain is surrounded by 3 of these membranes

what is cerebrospinal fluid (CSP)

the space between the inner 2 meninges is filled with this fluid, which is a shock absorber

meningitis

inflammation of the meninges

structure of the brain

cerebrum, cerebellum, thalamus, hypothalamus, medulla oblongata

cerebrum - structure

• divided into irght and left cerebral hemispheres

• grey matter = nerve cells, white matter = axons (many nerves

cerebral cortex

outer layer of the cerebrum

the cerebrum controls

muscles (voluntary movements), senses, learning, understanding

the cerebellum controls

• muscular coordination

• balance

thalamus - function

sends all incoming impulse to correct part of the brain

hypothalamus - function

• regulates the internal environment (homeostasis)

medulla oblongata controls

involuntary actions such as breathing and coughing

neuron

nerve cell

parts of a neuron

• dendrites

• axons

• schwann cells

• myelin

• cell body

• axon terminals

• neurotransmitter swellings

dendrites

carry impulses towards cell body

axons

carry impulses away from cell body

schwann cells

produce the myeline sheath

myelin

insulates the electrical impulses

cell body

contains nucleus and cell organelles

axon terminals

carry an impulse to a swelling called a neurotransmitter swelling

neurotransmitter swellings

release neurotransmitters that carry the impulse from one nerve cell to another

types of neurons

• sensory neurons

• interneurons

• motor neurons

sensory neurons

carry impulses to the CNS

interneurons

carry impulses between sensory and motor neurons

motor neurons

carry impulses away from the CNS

synapse

region where 2 neurons come into close contact

synaptic cleft

the tiny gap between the 2 neurons at a synapse

neurotransmitters include

• acetylcholine

• endorphins

• dopamine

lifestyle choices impacting endorphin and dopamine levels

• non-medical drug use

• exercise

• dietary choices

normal nerve path

stimulus - sensory neuron - spinal cord - brain - spinal cord - motor neuron - response

reflex action

an automatic, involuntary, unthinking response to a stimulus

role of a reflex action

to protect the body

path of a reflex action

stimulus - sensory neuron - spinal cord - interneuron - motor neuron - response

examples of reflex actions

the knee jerk, blinking

advantages of reflex actions

very fast response and protects the body from harm

inhibiting the breakdown of neurotransmitters

inhibiting the enzyme that inactivate acetycholine

preventing the reuptake of a neurotransmitter

drugs called selective seretonin reuptake inhibitors (SSRIs) treat depression by inhibiting the reuptake of serotonin at synpases in the brain

psychoactive drugs

they increase amounts of natural neurotransmitters or inhibits the reuptake of neurotransmitters

painkillers

they bind to pain receptors in post-synaptic neurons in the brain and block pain