Nervous system and coordination (eyeeeee)

function of the nervous system

coordinate and regulate bodily functions

function of the medulla oblongata

controls involuntary actions — heartbeat, peristalsis, rate of respiratory movement, contraction and dilation of blood vessels

function of cerebrum

• memory

• senses

• reasoning and decision making

cerebellum function

• control muscle coordination

• maintain body balance

hypothalamus function

1. regulate body temperature

2. control appetite

3. control sleep

4. control emotion

what are the nerves in the brain?

cranial nerves

compare voluntary vs involuntary actions and how they are different (3)

voluntary — action that can be controlled one’s conscious will

involuntary — action that cannot be controlled by one’s conscious will

V: brain is involved since impulse is initiated by the brain

IV: brain isnt involved FOR SPINAL REFLEX ONLY

V: speed of nerve impulse transmission is slower

IV: speed of nerve impulse transmission is faster

V: sensory neurone is not involed

IV: sensory neurone may be involved in reflex action

where and white and grey matter found in the spinal cord and the brain

spinal cord

White matter is in the outer portion

Grey matter is in the central portion of the

brain

white matter is found in the central portion

grey matter is found in the outer portion

what does the spinal cord consist of (6)

spinal nerve

dorsal root (with ganglion)

• sensory neuron

ventral root

• motor neuron

central canal

• contains cerebralspinal fluid

grey matter

white matter

where are the cell bodies of the sensory, relay and motor neurones found in the spinal cord

relay neurone and motor neurone: in the grey matter

sensory neurone: ganglion in the dorsal root

anatomy of a sensory neuron

• (one) dendron

• cell body

• axon

• myelin sheath

• axon terminal

long boi

anatomy of a relay neuron

• dendrite (long ahh dendrites)

• cell body

• axon terminal

no myelin sheath

anatomy of a motor neuron

• dendron (one dendron with myelin sheath)hatw

• cell body

• axon

• axon terminal

• myeline sheath

function of the three neuron types

1. sensory neurone - transmit impulse from the receptor to the relay neurone

2. relay neurone - links sensory neurone to motor neurone and transmits impulses from the sensory neurone to other parts of the CNS

3. motor neurone - transmits impulses from relay neurone to effector (muscles or glands)

what are nerves

bundle of nerve fibres enclosed in a sheath of connective tissue

what kind of fibres are contained by spinal nerves and what do they contain?

they contain mixed fibres because they are made up of sensory and motor nerve fibres

what does grey and white matter contain?

grey — cell bodies

white — nerve fibres of neurones

why are dendrites and axon terminals highly branche?

increase SAV ratio so that dendrites can form more connections with other neuron’s and axon terminal forms more connections with other neurons or effectors

what does the dendron and the axon do

dendron — transmit nerve impulse towards cell body

axos — transmit nerve impulse away from cell body

what are the two types of reflex action and how do they work

1. spinal reflex

   1. controlled by spinal cord

2. cranial reflex

   1. controlled by the brain and usually occur in the head region

what is reflex action

an immediate, automatic response to a specific stimulus without the conscious control of the will

what are spinal reflexes and cranial reflexes

spinal reflexes are controlled by the spinal cord

cranial reflexes are controlled by the brain

what is a reflex arc

the shortest nervous pathway in which impulses can travel from receptor to effectors, it includes the following

what does a reflex arc involve

1. receptor

2. sensory neurone

3. reflex centre

4. motor neurone

5. effector (gland or muscle)

what is a synapse and how does it work

1. the junction between 2 neurones

2. impulses are transmitted from an axon to a dendron across a synapse

3. transmission across a synapse is by chemical means through neurotransmitters

what is a stimulus

the change in environment that is detected by receptors, which are special sensitive tissues or sensory organs

what is a response?

it is brought about by an effector. it is a reaction a specific stimulus

what is a nerve impulse?

an electrical signal that transmitted along a neurone

what is a nerve fibre

a strand of cytoplasm extending from the cell body

compare the structures of sensory neurone and motor neurone

length of fibre;

sensory neuron has a long dendron and a short axon

motor neurone has a short dendron and a long axon

shape of cell body

sensory neurone has a circular cell body

motor neurone has an irregularly-shaped neurone

what are the similarities between a voluntary action and a reflex action/

both insole nerve impulses through neurones to an effector

what are the differences between nerves and hormones in controlling processes within the body

1. nerves involve nerve infuses and chemical neurotransmitters as signals while hormonal control involve hormones (chemical substances as signals)

2. electrical messages are transmitted along nerve fibres in neurones while hormones are transport by the blood

3. nervous controls → quick response while hormonal control → slow response

4. N → effect of message usually lasts a very short while, H → effect of message usually lasts longer

5. N → may be voluntary or involuntary h → always involuntary

6. Nervous → localised Hormonal → affect more than one target organ

structure and function of cornea in the eye

refracts light rays into the eye (greatest refrain of light rays)

dome-shaped transparent layer continuous with the sclera that covers over the pupil

function of the eyelid

protects cornea from mechanical damage and prevents excessive entry of light which may damage the retina

function of the tear gland

secretes tears to

1. wash away dust particles

2. moistens cornea for atmospheric yen to dissolve so the dissolved oxygen can diffuse into the cornea

3. lubricate the conjunctiva

eyelash function

shields the eye from dust particles

pupil function and structure

allows entry of light to reach retina 9because it is a hole)

size is controlled by iris muscles

conjunctiva function and structure

a transparent, mucus membrane covering the sclera

secretes mucus to keep the front of the eyeball moist

what layers does the eyeball have

1. sclerotic coat /sclera

2. choroid

3. retina

lens function and structure

transparent, circular, and bioconvex structure

its elastic and changes its shape / thickness to focus light onto the retina

retina structure and function

light-sensitive on which images are formed and contains light-sensitive cells or photoreceptors (connected to the nerve endings from the optic nerve)

fovea structure

small yellow depression in the retina, directly behind the lens

contains the greatest concentration of cones and no rods

enables person to have detailed colour vision in bright light

vitreous humour structure and function

transparent, jelly-like substance

keeps the eyeball firm and is transparent to help refract light onto the retina

suspensory ligament structure and function

connective tissue that attaches the edge of the lens to the ciliary body

ciliary body structure and function

thickened region at the from end of the choroid, which contains the clearly muscles

control curvature or thickness of the lens

blind spot structure

optic nerve levees the eye here

it does not contain androids or cones (not sensitive to light)

what are the functions of cones and what type of cones are there?

• red, blue and green (contains different pigments)

• see a variety of colours in bright light.

what are the function of rods?

• Rods are stimulated even by very dim light.

• see in dim light, but only in black or white. 

• Rods contain a pigment called visual purple. Vision purple becomes bleached when exposed to bright light and impulses cannot be sent to the brain.

what is accommodation?

The curvature or thickness of the lens of the eye is adjusted so that light rays can focus on the retina, enabling clear images of the objects at different distances to be formed on the retina.

how do eyes focus on nearby objects?

1. ciliary muscles contract, relaxing their pull on suspensory ligaments

2. suspensory ligaments slack, relaxing their pull on the lens

3. lens becomes thicker and more convex

4. light rays are sharply focused on the retina, stimulating the photoreceptors

5. nerve impulses generated are transmitted to the brain via the optic nerve

6. the brain interprets the impulses an the person sees the near object clearly

how do eyes focus on far away objects?

1. ciliary muscles relax, pulling on suspensory ligaments

2. suspensory ligaments become taut, pulling on the edge of the lens

3. lens becomes thinner and less convex

4. light rays are sharply focused on the retina, stimulating the photoreceptors

5. nerve impulses generated are transmitted to the brain via the optic nerve

6. the brain interprets the impulses an the person sees the near object clearly

how does the iris work?

in bright light, circular muscles contract and radial muscles relax, causing the size of pupil to constrict and this reduces the amount of light entering the eye

vice versa

how does pupil reflex work?

stimulus: change in light intensity

receptor: retina

sensory neurone in the optic nerve

brain

motor neurone

effector (iris)

how does refraction in eye work/

1. light rays are refracted through the cornea and the aqueous humour onto the lens

2. the lens causes further refraction and the rays are brought to a focus on the retina

3. image on the retina stimulates either the rods or the cones, depending on the intensity of the light

4. the image famed on the retina is upside down, laterally inverted, and diminished

how does a nervous impulse transmit across a synapse?

Electrical impulse arrives at axon terminal of cell X

Causes vesicles to migrate to membrane.

Neurotransmitters released into synaptic cleft

Neurotransmitters are fit into receptors on the membrane of Cell Y.  (and trigger the generation of electrical impulse in Cell Y)

Suggest how the structure of a synapse ensures that impulses travel in one direction.

S1: Neurotransmitters are released only from the vesicles in the presynaptic neurone. 

S2: Receptor molecules for the neurotransmitters are found only on the postsynaptic neurone. Therefore, impulses can only pass from the presynaptic neurone to the postsynaptic neurone.

adaptation of neurone

1. long serve fibre → nerve fibre travel long distances from spinal cord to effector

2. nerve fibre is surrounded by myelin sheath → insulated nerve fibre and increase the speed of nerve impulse transmission

3. ends of nerve cel is highly branched → receive nerve impulse /signal from other neuron’s

how will the photoreceptors on the retina be stimulated by the increased light intensity?

• producing nerve impulses to be transmitted to the brain for pupil reflex to take place;

how is increased eye pressure detrimental?

will damage /destroy the retina /optic nerve