Nervous System Flashcards
coordinated response requires ……………..
a stimulus, a receptor and an effector
central nervous system consists of …………..
brain and spinal cord
central nervous system is linked to sense organs by ……….
nerves
Peripheral nervous system is composed of:………..
peripheral nerves
Peripheral nervous system contains:
sensory neurons
motor neurons
Function of PNS
sends information to CNS from receptors
carries instructions from CNS to effectors
Function of CNS
receives information from PNS, processes this and sends instructions to PNS
cells specialised for transmitting impulses
neurons
motor neuron
cell body in spinal cord (CNS)
transmits impulses from relay or sensory neurons to effectors
sensory neuron
cell body just outside spinal cord (CNS)
transmits impulses from receptors to relay or motor neurons
relay neuron
found in CNS
relays impulses from sensory to motor neurons
a synapse between a motor neuron and muscle
neuromuscular junction
State two features that distinguish motor neuron
from other types of nerve cell
cell body in spinal cord (CNS)
transmits impulses from relay or sensory neurons to effectors
…………is a change in an animal’s surrounding, ……….. is the reaction to that change
Stimulus, response
A tiny electrical signal that passes down a nerve cell caused by movements of ions in and out of the axon
nerve impulse
The biological name of a nerve cell…………
neurone
Synapse of a nerve cell on a muscle
neuromuscular junction
covering made of a lipid material that surrounds an axon .
myelin sheath
What is myelin sheath and what is its function?
covering made of a lipid material that surrounds an axon . Nerve cells that have myelin sheath are described as myelinated.
its function is to insulate the axon preventing short circuits with other axons
Extension of the cytoplasm of a neurone that carries impulses towards the cell body
dendron
Fine extensions of the dendron of the neurone
dendrites
junction between two neurones
synapse
long extension of a neurone that carries nerve impulses in a direction away from the cell body.
axon
a middle layer of the skin containing many sensory receptors
dermis
The diagram shows a horizontal section through the human eye. Which is the retina?
A,B,C or D ?
C
White tough outer coat of the eye
Sclera
colour-sensitive receptors are concentrated here
fovea
Controls how much light enters the eye by changing size of pupil
iris
contains light receptors, some sesitive to light of different colours
retina
a trasparent layer that refracts light
cornea
hole that allows light into the eye
pupil
carries nerve impulses to the brain
optic nerve
refracts light to focus it onto retina
lens
What are the two types of receptor cells in the retina ?
Rods which are sensitive to dim light
Cones which distinguish between different colours in bright light
The role of the iris is to control the amount of light entering the eye. Explain how.
The iris contains two types of muscles. circular muscles form a ring shape in the iris and radial muscles lie like the spokes at a wheel. In bright light the pupil is constricted(made smaller) . This happens because the circular muscles contract and the radial muscles relax. in dim light the opposite happens.
How does the Iris Reflex Work?
The iris contains two types of muscles. circular muscles form a ring shape in the iris and radial muscles lie like the spokes at a wheel
in bright light:
- Photoreceptors detect change in environment ( bright light)
- circular muscles contract
- radial muscles relax
- pupil constricts (made smaller)
- Less light enters the eye
in dim light:
- Photoreceptors detect change in environment ( dim light)
- circular muscles relax
- radial muscles contract
- pupil dilates (made wider)
- more light enters the eye
for the attached image choose the correct answer,
A-Radial muscles relax, circular muscles relax
B-Radial muscles relax, circular muscles contract
C-Radial muscles contract, circular muscles relax
D-Radial muscles contract, circular muscles contract
D
Controls shape of lens with ciliary muscles
ligaments
Has no receptors
Blind spot
Controls shape of lens to allow focusing
Ciliary muscles
Describe the structure and function of the eye as a receptor
A bundle of neurones is known as a ……
nerve
changes taking place in the eye which allow it to focus on objects at different distances
accommodation
Draw and describe the structure and the function of sensory neurones
Sensory neurones carry impulses from sense organs to the CNS
Sensory neurones are long and have a cell body branching off the middle of the axon
Draw and describe the structure and the function of sensory neurones
Relay neurones are found inside the CNS and connect sensory and motor neurones
Relay neurones are short and have a small cell body at one end with many dendrites branching off it
Draw and describe the structure and the function of motor neurones
Motor neurones carry impulses from the CNS to effectors (muscles or glands)
Motor neurones are long and have a large cell body at one end with long dendrites branching off it
nerve pathway of a reflex action
reflex arc
rapid, automatic involuntary response to a stimulus.
reflex action
There are 3 types of cone cells which are sensitive to different colours of light which colours?
(red, blue and green)
inner, light-sensitive layer at the back of the eye
retina
Explain how the eye focuses on objects at different distances (Accommodation)
When focusing on a nearby object
- Ciliary muscles contract
- Suspensory ligaments slacken
- This allows lens to become rounded
- Light is refracted more by the lens allowing the eye to focus on the nearby object.
when focusing on a distance object
- Ciliary muscles relax
- Suspensory ligaments pulled tight
- This allows lens to become thinner ( flat )
- Light is refracted less by the lens allowing the eye to focus on the distance object.
What are the retina two types of light receptors
rods and cones
What is the funciton of rod cells
- work in dim light (night vision)
- detect black and white
- don’t give a clear image
- found all over the retina, but few in fovea (and none in blind spot!)
What is the funciton of cone cells?
- need bright light to work
- three types – detect green, red and blue light (colour vision)
- give a clear image
- concentrated in fovea (and none in blind spot!)
Why is this reflex action important?
stops retina from being damaged in bright light
allows maximum light into the eye to see in dim conditions
Why do we have reflex actions?
Reflex actions
- are rapid
- do not involve a nerve impulse being passed to the brain – this saves time
- are there to protect us – we can react rapidly to a stimulus that may harm us
Which of these statements about neurones is correct?
A-Relay neurones conduct nerve impulses from motor neurones to
sensory neurones.
B-Motor neurones conduct nerve impulses to muscle fibres.
C-Sensory neurones conduct nerve impulses to sense organs.
D-Receptor cells stimulate motor neurones to conduct impulses.
B
When a bright light is shone into the eye, the diameter of the pupils changes. Which is the correct explanation of this effect?
A-The diameter of the pupils decreases to protect the retina from damage.
B-The diameter of the pupils widens to increase the field of view.
C-The diameter of the pupils decreases to reduce the field of view.
D-The diameter of the pupils increases to allow more light to reach the retina.
B
Which answer describes what happens in the eye to adjust to light
from a near object?
A-Ciliary muscles contract to reduce the tension in suspensory ligaments and increase the curvature of the lens.
B-Ciliary muscles relax to reduce the tension in suspensory ligaments and decrease the curvature of the lens.
C-Ciliary muscles contract to increase the tension in suspensory ligaments and increase the curvature of the lens.
D-Ciliary muscles relax to increase the tension in suspensory ligaments and decrease the curvature of the lens.
Define “gland”:
group of cells / organ that releases (secretes) a substance
What are the two types of gland?
How are they different?
Exocrine gland
e.g
- salivary gland
- pancreas (releasing digestive enzymes)
Endocrine gland (ductles) e.g.
- adrenal gland
- pancreas (releasing hormones)
How does the hormone know what is its target organ?
•cells from target organ have a specific receptor for the hormone à binds and causes its effects
Hormonal control of responses
- hormone is released from a gland into blood capillaries
- hormone travels through blood vessels until it reaches its target organ/s
- hormone causes an effect in the target organ
Adrenaline (p100-1/watch the video):
- what are its target organs?
- what response does it cause in each?
Many drugs act at synapses
Caffeine – stimulant
causes more neurotransmitter release
Heroin – narcotic (blocks pain)
blocks neurotransmitter binding sites on pain-sensing nerve paths
Toxins/nerve gases – block synapses between motor neurons and muscles – cause paralysis
Synapses ensure nerve impulses travel in one direction only
True / False
True
voluntary response is
one where you make a conscious decision to carry out a particular action therefore it starts with your brain
An involuntary (or reflex) response
does not involve the brain as the coordinator of the reaction and you are not aware you have completed it until after you have carried it out
Involuntary actions are usually ones which are essential to basic survival and are rapid, whereas voluntary responses often take longer as we consider what the response might be before doing it
Describe the actions of a reflex
A reflex
(Automatic
Fast
Protective)
- The pin (the stimulus) is detected by a pain/pressure/touch receptor in the skin
- Sensory neurone sends electrical impulses to the spinal cord (the coordinator)
- Electrical impulse is passed on to relay neurone in the spinal cord
- Relay neurone connects to motor neurone and passes the impulse on
- Motor neurone carries impulse to a muscle in the leg (the effector)
- The muscle will contract and pull the foot up and away from the sharp object (the response)
Stimules - Receptor - Sensory Neurone - Reley Neurone - Motor Neurone - Effector - Response
The junction between two neurones is known as a
synapse
How an Impulse is Passed Across a Synapse
- Neurones never touch each other
- The junctions (gaps) in between them are called synapses
- The electrical impulse travels along the first axon
- This triggers the nerve-ending of the presynaptic neurone to release chemical messengers called neurotransmitters from vesicles which fuse with the presynaptic membrane
- The neurotransmitters diffuse across the synaptic gap and bind with receptor molecules on the membrane of the second neurone (known as the post synaptic membrane)
- This stimulates the second neurone to generate an electrical impulse that travels down the second axon
- The neurotransmitters are then destroyed to prevent continued stimulation of the second neurone which would cause repeated impulses to be sent
- Synapses ensure that impulses only travel in one direction, avoiding confusion within the nervous system if impulses were travelling in both directions
- As this is the only part of the nervous system where messages are chemical as opposed to electrical, it is the only place where drugs can act to affect the nervous system - eg this is where heroin works
The only place where drugs can act to affect the nervous system
Synapses ( as chemical messages ) not electrical
A few examples of reflex action are:
- When light acts as a stimulus, the pupil of the eye changes in size.
- Sudden jerky withdrawal of hand or leg when pricked by a pin.
- Coughing or sneezing, because of irritants in the nasal passages.
- Knees jerk in response to a blow or someone stamping the leg.
- The sudden removal of the hand from a sharp object.
- Sudden blinking when an insect comes very near to the eyes.
staring at your hand right in front of your eye will make your eyes feel tight and staring at an object far away feels relaxing and comfortable
explain why
staring at your hand right in front of your eye will make your eyes feel tight after a few seconds. This is because the ciliary muscles are contracted**. Staring at an object far away feels relaxing and comfortable **because the ciliary muscles are relaxed.
what is is the role of liver with the The Endocrine System?
The liver regulates levels of hormones in the blood; transforming or breaking down any that are in excess.
How do hormones transport around the body?
illustrate using a diagram
- Endocrine glands have a good blood supply as when they make hormones they need to get them into the bloodstream (specifically the blood plasma) as soon as possible so they can travel around the body to the target organs to bring about the response
- Hormones only affect cells with target receptors that the hormone can bind to. These are either found on the cell membrane, or inside cells. Receptors have to be complementary to hormones for there to be an effect.
- The liver regulates levels of hormones in the blood; transforming or breaking down any that are in excess.
list some important hormones in the body
list of effects of adrenaline on the body
drenaline is known as the fight or flight hormone as it is produced in situations where the body may be in danger
It causes a range of different things to happen in the body, all designed to prepare it for movement (ie fight or flight).
These include:
Increasing blood glucose concentration for increased respiration in muscle cells
Increasing pulse rate and breathing rate so glucose and oxygen can be delivered to muscle cells, and carbon dioxide taken away, from muscles cells more quickly
Diverting blood flow towards muscles and away from non-essential parts of the body such as the alimentary canal; again to ensure the reactants of respiration are as available as possible
Dilating pupils to allow as much light as possible to reach the retina so more information can be sent to the brain
Why Adrenaline cause a dilating pupils?
To allow as much light as possible to reach the retina so more information can be sent to the brain
Compare between Nervous & Hormonal Control
How does the hormone know what is its target organ?
•cells from target organ have a specific receptor for the hormone à binds and causes its effects
What is Insulin?
- hormone released from the pancreas
- lowers blood glucose concentration
- allows (liver) cells to take up glucose à glycogen formed
What happens if not enough glucose in the blood?
- hypoglycaemia
- body can lose consciousness and go into a coma
What happens if too much glucose in the blood (can also be detected in the urine?
- hyperglycemia
- causes severe dehydration (& thirst)
- can be dangerous (causes ketoacidosis)
- longer-term, can damage blood vessels
Type 1 diabetes:
- insulin-producing cells in the pancreas are destroyed
- no insulin produced
- glucose remains in the blood (ends up in urine à detected – link to kidney function)
- glucose remains in the blood (ends up in urine à detected – link to kidney function)
- (thought to be) an autoimmune disease
tissue in the piter part of the spinal cord and inner part of the brain consist mainly of myelin sheath
A. White Matter
B. Grey Matter
C. Synapse
D. ventral root
A. White Matter
tissue in the middle of the spinal cord and outer part of the brain consist mainly of nerve cell bodies
A. White Matter
B. Grey Matter
C. Synapse
D. ventral root
A. White Matter
