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Biology 🦠 > Chapter 10: Nervous system and the eye > Flashcards

Chapter 10: Nervous system and the eye Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What is a stimulus

A

A change in the environment that causes an organism to react. An organism’s reaction to a stimulus is called a response

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2
Q

What is sesitivity

A

The ability to respond to a stimulus

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3
Q

Role of nervous system

A

regulates bodily functions and activities; and how we react to our surroundings

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4
Q

Components of nervous system

A
  1. Central Nervous System (CNS): brain & spinal cord
  2. Peripheral Nervous System (PNS): Cranial nerves (from brain) , spinal nerves (from spinal cord), sense organs
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5
Q

Types of neurones

A
  1. Sensory neurone (receptor neurone)
  2. Relay neurone (intermediate neurone)
  3. Motor neurone (effector neurone)
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6
Q

Sensory neurone

A

Transmits nerve impulses from sense organs or receptors to the CNS

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7
Q

Relay neurone

A

Transmits nerve impulses from the sensory neurone to the motor neurone. They are found in the CNS

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8
Q

Motor neurone

A

Transmits nerve impulses from the CNS to the effectors

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9
Q

Structure of motor neurone

A
  1. Cell body: contains a nucleus, cytoplasm, cell membrane and organelles. It’s irregular in shape
  2. Nerve Fibre: A strand of cytoplasm extending from the cell body
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10
Q

Structure of sensory neurone

A
  1. Cell Body: Circular
  2. Nerve fibre: one long one extending towards receptor and one short one extending towards the relay neurone in CNS
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11
Q

What is a synapse

A

The junction between 2 neurones. Nerve impulses are transmitted across the synapse by chemicals released by the neurones

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12
Q

How do the brain, spinal cord and spinal nerves work tgt

A
  1. In spinal cord, relay neurones may synapse w/ sensory & motor neurone. They transmits nerve impulses from the sensory neurones to the motor neurones in reflex action
  2. Relay neurones synapse w/ sensory neurones and transmit nerve impulses up spinal cord to the brain. This causes sensations
  3. Relay neurones may transmit nerve impulses about a voluntary action from brain, down spinal cord
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13
Q

Nerve impulses pathway (sensation)

A

Receptor in skin ➡️ sensory neurone ➡️ Relay neurone in spinal cord ➡️ Brain

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14
Q

Nerve impulses pathway (Voluntary action)

A

Brain ➡️ Relay neurone in the spinal cord ➡️ Motor neurone ➡️ Effector

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15
Q

What is reflex action?

A

An immediate response to a specific stimulus without conscious control

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16
Q

Types of reflex actions

A
  1. Cranial reflexes: Controlled by brain and usually occur in head region (Ex: Pupil reflex)
  2. Spinal reflexes: Controlled by the spinal cord, occurs below the neck (Ex: Knee-jerk reaction)
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17
Q

What happens when your hand touches a hot object (for example)

A
  1. Touch and pain receptors in the hand will detect the hot object (stimulus)
  2. Receptors in the skin are stimulated and produces nerve impulses
  3. Sensory neurone transmits the nerve impulses produced to the spinal cord
  4. In the spinal cord, nerve impulses are transmitted first across a synapse to the relay neurone, and then across another synapse to the motor neurone
  5. Motor neurone transmits the nerve impulses from spinal cord to the effector, which is the hand muscles
  6. Muscles in hand contracts and the hand moves away from hot object
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18
Q

What is reflex arc

A

It is the shortest pathway by which nerve impulses travel from the receptor to the effector in a reflex action

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19
Q

Pathway of nerve impulses (reflex arc)

A

Receptor ➡️ Sensory neurone ➡️ Relay neurone (CNS) ➡️ motor neurone ➡️ effector

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20
Q

External structure of eye

A
  1. Sclera
  2. Conjunctiva
  3. Eyelashes
  4. Tear Gland
  5. Eyelids
  6. Iris
  7. Pupil
21
Q

Sclera

A
  • “white” of eye
  • tough, white outer covering of the eyeball
  • is continuous with the cornea
  • protects the eyeball from mechanical damage
22
Q

Conjunctiva

A
  • thin transparent membrane covering sclera in front
  • a mucous membrane
  • secretes mucus, help keep front of eyeball moist
23
Q

Eyelashes

A
  • shields the eye from dust particles
24
Q

Tear gland

A
  • lies at the corner of the upper eyelid
  • secretes tears that wash away dust particles; keep cornea moist; and lubricate the conjunctiva to reduce friction when eyelids move
25
Q

Eyelids

A
  • protects the cornea from mechanical damage
  • squinting prevents too much light from entering the eye and damaging the retina
  • blinking spreads tears over the cornea and conjunctiva, and wipes dust particles off the cornea
26
Q

Iris

A
  • a circular sheet of muscles
  • controls the sizes of the pupil 👉 controls amount of light entering eye
  • contains pigment that gives the eye its colour
27
Q

Pupil

A
  • a hole in the centre of the iris
  • allows light to enter the eyes
28
Q

Internal structure of eye

A
  1. Retina
  2. Lens
  3. Blind Spot
  4. Optic Nerve
  5. Fovea
  6. Vitreous Chamber
  7. Choroid
  8. Ciliary Body
  9. Suspensory ligament
  10. Cornea
  11. Aqueous Chamber
29
Q

Retina

A
  • innermost layer of the eyeball
  • light sensitive layer on which images are formed
  • contains photoreceptors
  • photoreceptors are connected to nerve endings from optic nerve
30
Q

Lens

A
  • transparent, circular and biconvex structure
  • it is elastic
  • changes its thickness to focus light onto the retina
31
Q

Blind Spot

A
  • region where the optic nerve leaves the eye
  • does not contain any rods or cones 👉 it’s not sensitive to light
  • one will not be able to see an object if the image falls into the blind spot
32
Q

Optic nerve

A
  • nerve that transmits nerve impulses to the brain when the photoreceptors in the retina are stimulated
33
Q

Fovea

A
  • small yellow depression in retina
  • situated directed behind the lens
  • where images are normally focused
  • contains greatest concentration of cones, but not rods
  • enables a person to have detailed colour vision in bright light
34
Q

Vitreous chambre

A
  • space between the lens
  • filled with vitreous humour (a transparent, jelly-like substance)
  • vitreous humour keeps the eyeball firm and helps to refract light onto the retina
35
Q

Choroid

A
  • middle layer of the eyeball (in between sclera and retina)
  • pigmented black to prevent internal reflection of light
  • contains blood vessels that bring oxygen and nutrients to eyeball and remove metabolic waste products
36
Q

Ciliary body

A
  • thickened region at the front end of the choroid
  • contains ciliary muscles, which controls the curvature/thickness of the lens
37
Q

Cornea

A
  • dome-shaped transparent layer continuous with the sclera
  • refracts light rays into the eye
  • causes greatest refraction of light into the eye
38
Q

Aqueous chamber

A
  • space between lens and cornea
  • filled with aqueous humour (a transparents, watery fluid)
  • aqueous humour keeps front of the eyeball firm and helps to refract light into the pupil
39
Q

What is pupil reflex

A
  • a reflex action that causes pupils to change in size in response to changes in light intensity
  • controlled by iris
40
Q

Benefits of pupil reflex

A
  1. it is automatic, so no learning is required
  2. prevents excessive light from entering the eye and damaging the retina
  3. it is an immediate response
  4. allows enough light to enter the eye to let us see
41
Q

How iris control amount of light entering our eyes?

A
  • using circular and radial muscles
  • they are antagonistic muscles
42
Q

What happens in bright light?

A
  • size of pupil decreases 👉 less light enters the eye
  • circular muscles contract
  • radial muscles relax
    ( when it’s bright, happy marriage, hence CC and RR)
43
Q

What happens in dim light?

A
  • size of pupil increases 👉 more light enter eye
  • circular muscles relax
  • radial muscles contract
    (when it’s dim, life is sad, there is a divorce, hence CR and RC)
44
Q

Nerve impulses pathway for pupil reflex

A

Stimulus (Change in light intensity) ➡️ Receptors (Retina) ➡️ Sensory neurone in optic nerve ➡️ Brain ➡️ Motor neurone ➡️ Effector (Iris Muscles)

45
Q

How do we see

A
  1. light rays are refracted through the cornea and the aqueous humour onto the lens
  2. lens causes further refraction and the rays are brought to a focus on the retina
  3. the image on the retina stimulates either the rods or cones, depending on intensity of light
    - image formed on retina is inverted, laterally inverted and diminished
46
Q

What is focusing

A
  • adjustment of the lens of the eye so that clear images of objects at different distances are formed on the retina
47
Q

Focusing on distant objects

A
  1. ciliary muscles relax, pulling on suspensory ligament (CR)
  2. Suspensory ligament become taut, pulling on edge of lens (ST)
  3. Lens becomes thinner and less convex
  4. Light rays from the distant object are sharply focused on the retina
  5. Photoreceptors are stimulated
  6. Nerve impulses produced are transmitted by the optic nerve to the brain. The brain interprets the nerve impulses and the person sees the distant object.
48
Q

Focusing on near objects

A
  1. Ciliary muscles contract, relaxing their pull on the suspensory ligaments (CC)
  2. Suspensory ligament slacken, relaxing their pull on the lens (SS)
  3. The lens, being elastic, becomes thicker and more convex
  4. Light rays from the near object are sharply focused on the retina
  5. Photoreceptors are stimulated
  6. Nerve impulses are transmitted by the optic nerve to the brain. The brain interprets the nerve impulses and the person sees the near object

Biology 🦠 (18 decks)

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