Chapter 21 - Nervous Control And Drugs Flashcards
Coordinating systems
- nervous systems
- endocrine system
The human nervous system
- consist of two parts - the CNS and the PNS
- CNS consist of brain and spinal Cord and PNS consist of nerves
- the NS consist of the brain, spinal cord and nerves
Define nerve cells
Are special cells that are adapted to conduct messages in form of electrical signals though the nervous system
Structure and function of motor nerve cells
- found between CNS and effector
- has cell body at the end
- has very long axon along impulses travel
- has a fatty myelin sheath to insulate and prevent leakage
- have Schwann cells which produce the myelin sheath
- nodes of Ranvier which increase speed
- have dendrites which transmits impulses to the cell body
- function : conduct electrical impulses from CNS to muscles
Structure and function of sensory nerve cells
- found between receptors and CNS
- has cell body more to the middle
- has short axon along which impulses travel away from cell body
- have a long dendron along which impulses travel to the cell body
- has a fatty myelin sheath to prevent leakage
- have Schwann cells that produces the myelin sheath
- the node of Ranvier speed up impulses
Describe effectors in terms of muscle and glands
- effectors respond to stimuli
- receive impulses from motor nerve cell
- ensures the correct response will take place
- muscles contract and relax to cause the correct movement
- while glands secrete the correct hormones
Reflex actions
- happens without you thinking about it
- serves as a protective system against injury
- a rapid response
- an automatic response
- an inborn response
Reflex arc
- stimulus received by receptor
- stimulus converted to nerve impulse
- impulse conduct along sensory nerve
- impulse conducted from sensory along relay neuron to motor nerve
- motor conducts impulse to effector
- effector makes correct response
Structure of the synapse
- the point where two ends meet
- consist of a presynaptic neuron and a postsynaptic neuron
- neurons do not touch, have small gap called the synaptic cleft
- presynaptic contains vesicles with neurotransmitters, many mitochondria to release energy and a presynaptic membrane
- postsynaptic has postsynaptic membranes and has receptor sites
Transmission of nerve impulses across synapse
- impulses reach synaptic knob of presynaptic
- Calcium channels open in presynaptic
- Ca ions enter presynaptic
- vesicles with neurotransmitters (acetylcholine) move towards presynaptic
- vesicles fuse with membrane and release neurotransmitters into cleft
- diffuses across cleft
- neurotransmitters bind with receptor proteins on postsynaptic
- receptor changes shape, channels open and sodium ions enter postsynaptic
- postsynaptic becomes depolarised
- nerve impulse generated in postsynaptic
Define drugs
- chemical substances that affects the CNS causing changes in behaviour and addiction
Effects of opiate drugs at synapses
- blocks neurotransmitters from being released
- fewer impulses reach effector
- feels numb and sleepy
- can be used as pain killers
Define a sense organ
- groups of special receptor cells which detects changes
Name sense organ and sense that is stimulated by light
- eye
- sight
Name the sense organ and stimulus associated with hearing
- ear
- sound
Name the stimulus and sense of the nose
- chemicals
- smelling
Name the sense organ and sense stimulated by chemicals
- tongue
- tasting
What sense organ is affected by temperature and pressure
- the skin
Study structure of the eye
Page 364
Yeah you heard me !
Function of the sclera
Protects delicate Inner structures and provide attachment of muscle which moves the eye
Function of eye muscles
It moves the eyeball, holds it in place in the sockets
Function of the cornea
Allows light to enter and helps bend light
The conjunctiva
Prevents friction during blinking
Function of choroid
Reduces reflection inside the eye
What controls the curvature of the lens for near and far distant vision ?
The ciliary body
The suspensory ligaments
Holds the lens in position
Function of the iris
Forms the pupil and controls the size of the pupil
What is the function of the retina?
I don’t know, you tell me
What releases impulses when stimulated by light
The retina !!
Function of the yellow spot
Responsible for very sharp vision
What is the function of the optic nerve
Transmits impulses from the retina to the visual cortex of the cerebrum
The blind spot
Blood vessels enter and leave the eye at this spot
Fiction of the aqueous humour
Helps maintain curved shape of the cornea
The vitreous humour
Maintains the shape of the eye
Focusing on nearby objects
- ciliary muscles contract
- tension in suspensory muscles reduced
- lens has high elasticity
- lens becomes more convex
- causes more refraction of light
Focusing on distant objects
- The ciliary muscles relax
- more tension in suspensory ligaments
- the lens becomes less convex
- less refraction of light
The pupil reflex in bright light
- the circular muscles contract
- the radial muscles relax
- iris becomes larger and pupil constricts
- stops too much light from entering
The pupil reflex in dim light
- the circular muscles relax
- radial muscles contract
- iris becomes smaller and pupil dilates
- lets more light in
Describe the structure of retina
- possesses photoreceptors
- there are two types : rods and cones
- convert light energy into chemical energy
- cones found in centre of retina mainly in yellow spot
- cones found in peripheral area
Function of cones
- work in bright light
- it detects colour
- each cone is linked to one neuron and gives very sharp image
- cones more sensitive to light
Function of rods
- work in dim light
- don’t detect colour
- groups of rods are linked to one neuron does not give sharp image
Study table on page 371
Table shows differences between Rods and cones
Voluntary actions
- can be controlled
- involves decision
- not automatic
Involuntary actions
- actions which can’t be controlled
- it’s automatic
- no thought required
True or false :Antagonistic muscles works in pairs
True
Antagonistic muscles
- are voluntary
- one contacts and the other relaxes
- the muscles pull on the tendons to move the bones
Effects and dangers of alcohol abuse
- lead to drinking and driving
- cause irreversible destruction to liver cells
- is a dehydrating agent
- lead to blockage of capillaries
- lead to short term memory loss
Effects and dangers of dagga abuse
- easily develops mental dependence
- cause hallucinations
- causes paranoia
- acts as depressant drug
- increases heart rate
- can cause sterility
- contains carcinogens
Effects of nicotine abuse
- highly addictive
- reduces diameter of arterioles
- increases heart rate
- increases stickiness to blood platelets and increases risk for blood clots
Abuse of heroine
- causes feeling of pleasure
- due to use of needles can cause hepatitis and HIV
- can cause death
- can lead to respiratory failure
- veins can collapse
