The Nervous System Flashcards
Axon
The Long Part of a Nerve Cell along which the Electrical Signal quickly moves.
Central Nervous System (CNS)
The part of the Nervous System made up of the Brain and Spinal Cord.
Controls and coordinates responses between Receptors and Effectors - uses nerve impulses (electrical impulses) to react quickly to a stimulus.
Coordinator
The Brain or Spinal Cord (CNS)
Controls and coordinates responses between Receptors and Effectors.
Uses Nerve Impulses to react quickly to a stimulus.
Diameter
Length of a line that runs from one edge of a circle to another, passing through the centre.
Effector
The Organ, Tissue or Cell (Muscle or Gland) that produces a response.
Extremities
Furthest point of something, which in the body is the hands and feet.
Hormones
Chemical Messengers produced in Glands and carried by the Blood to Specific Organs in the body.
Motor Neurone
The Nerve Cell that carries Electrical Impulses from the CNS to effectors such as Muscles or Glands.
Neurone
Nerve cells.
Carries info in the form of nerve impulses from the receptor to the coordinator when stimulated.
Receptor
Organ, Tissue or Cell that detects a Stimulus.
Refraction
The bending of light as it passes from one substance into another.
(also happens with sound waves).
Retina
Light-sensitive area on the back of the eye.
Light must be focused on the retina in order to see clearly.
Sensory Neurone
Nerve cell that transmits electrical impulses from receptors in the Sense Organs to the CNS.
Spinal Cord
Part of Central Nervous System of a mammal which runs inside its backbone
Stimulus
Sends a signal - sets off a reaction in the Nervous System as a response to Environmental Changes detected by receptors in an organism.
E.g - light, heat, sound, gravity, smell, taste, or temperature.
Plural; Stimuli.
Synapse
Tiny gap at the junction between 2 nerve cells, which nerve signals must cross.
Transmit
Cause something to pass from 1 area to another.
Brain and Spinal Cord
= Form the Central Nervous System (CNS).
Hormonal System
Uses hormones to react slowly to a stimulus.
Different receptors are sensitive to?
Different stimuli
E.g. receptors in the eye are sensitive to light.
Receptors detect a Stimulus and send signals through…?
The Sensory Neurones.
Coordinator determines a correct response to a…?
Stimulus
Sensory Neurone transmits electrical impulses from…? To?
Receptors in the Sense Organs to the CNS
Motor Neurone carries Electrical Impulses from the CNS to?
Effectors such as Muscles or Glands.
Nerve Cells
Neurones
Nerve Cell Examples
Motor Neurone - carries electrical impulses from the CNS to effectors.
Sensory Neurone - transmits electrical impulses from receptors in the sense organs to the CNS.
Examples of Effectors
Muscles or Glands
Nervous System; Speed of reaction
Fast
Hormonal System; Speed of reaction
Slow
Nervous System; Nature of response
Electrical Impulses
Hormonal System; Nature of response
Hormones and Chemicals that travel in Blood.
Cornea
Transparent part at front of eye that allows light to enter.
Causes slight bending/refraction of light.
Pupil
Space in the iris that allows light into the eye.
Iris
Controls how much light enters the eye by changing its diameter.
Lens
Bends/refracts light towards the retina.
Aqueous Humour
Fluid in front of the lens that helps maintain the shape of the eye and lens.
Vitreous Humour
Fluid behind the lens that helps maintain the shape of the eye and lens.
Keeps the retina against the wall of the eye.
Optic Nerve
Contains Neurones that carry info from Eye to Brain.
Parts of the Eye
- Conjunctive
- Cornea
- Pupil
- Iris
- Lens
- Aqueous Humour
- Vitreous Humour
- Retina
- Optic Nerve
Eyes are specialised sense organs that
Contain receptors sensitive to light.
Ciliary muscle
Circular Ring of Muscle, surrounds the lens.
Lens is attached to the Ciliary muscle by
Suspensory Ligaments
When Focusing On a Distant Object
Muscle - Relaxes.
It’s Diameter - Becomes wider.
Suspensory Ligaments - Tighten, pulling the Lens thinner; as little adjustment is needed to focus light onto the Retina.
When Focusing On a Nearby Object
Muscle - Contracts
Diameter - Becomes smaller.
Suspensory Ligaments - Slacken causing the Lens to go back to its normal thicker shape; provides an additional refraction to focus light on the retina.
Too Little/Too Much Light Entering the Eye
Can damage the light sensitive receptor cells in the retina.
Dim Light Entering the Eyes
Pupil becomes larger - to allow as much light as possible to enter.
Bright Lights Entering the Eye
Pupil becomes smaller - to restrict the amount of light entering.
As light passes through the Cornea
Refraction takes place.
More refraction occurs when…
The light passes through the lens.
Looking at a distant object
Lens is thin as little adjustment is needed to focus light onto the retina.
Looking at nearby objects
Lens is thick to provide additional refraction to focus light on the retina.
Receptors and effectors are
Connected to the CNS by neurones.
Neurones function
Transmit electrical impulses across the NS quickly.
Neurone adaptations
Explained
- Cell body; contains cytoplasm & nucleus
- The axon - long extension of the cytoplasm (can be up to 1m).
- Means nerve impulses can be transmitted to the extremities by 1 cell.
- Myelin sheath; fatty layer that surrounds the axon.
Acts as an insulator and speeds up nerve impulses. - Branched ends of axon & the smaller branches coming from the cell body - allow the neurone to make connections with many other neurones.
Neurone adaptations -
Cell Body;
Contains cytoplasm & nucleus.
Neurone adaptations -
The Axon;
Long extension of the cytoplasm (can be up to 1m).
Means nerve impulses can be transmitted to the extremities by 1 cell.
Neurone adaptations -
Myelin sheath;
Fatty layer that surrounds the axon.
Acts as an insulator and speeds up nerve impulses.
Neurone adaptations -
Branched ends of axon and the smaller branches coming from the cell body;
Allow the neurone to make connections with many other neurones.
Neurone adaptations
Cell Body - contains Cytoplasm and Nucleus.
Axon - long extension of the Cytoplasm.
Myelin sheath - Fatty Layer that surrounds the Axon.
Branched ends of Axon and smaller branches coming from the cell body - allow the Neurone to make connections with many other Neurones.
What are Neurones adapted for;
To transmit electrical impulses across the NS.
Myelin sheath in Neurones
Acts as an insulator and speeds up nerve impulses.
Synapse
Junction between 2 neurones.
Electrical impulse cannot cross the small gap.
What can an electrical impulse not cross?
Small gap between neurones
Process to allow an electrical impulse to cross a synapse.
When impulse reaches end of an axon entering the synapse - axon releases transmitter substance.
- Transmitter substance diffuses across gap.
- When concentration of transmitter substance is high enough on the other side of the gap -
Impulse triggered in the next axon leaving the synapse.
-Electrical impulse continues on its way.
Where releases the transmitter substance?
Axon
What diffuses across a Synapse?
Transmitter Substance
Transmitter Substance
Chemical substance that transmits nerve/electrical impulses across a synapse.
Where is a synapse found?
Near the end of an axon.
Voluntary Actions
Involve conscious thought (thinking time).
Reflex Actions
Do not involve conscious thought - happen subconsciously
- And quickly to avoid unnecessary damage to the body.
Example of Reflex Actions
Rapidly removing your hand from a hot plate before it gets burned.
Why do reflect actions happen quickly?
The reflex pathway is kept short
- and involves smallest number of neurones and synapses possible.
How many Neurones and Synapses are involved in a reflex arc?
3 Neurones and 2 Synapses.
Involved in Reflex Arc:
Explained
3 Neurones + 2 Synapses.
The sensory neurone - carries info from receptor to spinal cord (coordinator).
The association neurone - joins sensory neurone and motor neurone.
The motor neurone - carries info from spinal cord to an effector that can cause a response.
Involved in Reflex Arc:
Simplified
3 Neurones + 2 Synapses.
- Sensory neurone
- Association neurone
- Motor neurone
Sensory Neurone
Carries info from receptor to spinal cord (coordinator).
Association Neurone
Joins sensory neurone and motor neurone.
Motor Neurone
Carries info from spinal cord to an effector that can cause a response.
What Neurones begin with the Cell Body?
Association and Motor Neurones.
Thickness of the lens can be adjusted
To focus light on the retina.
Conjunctiva
Thin, transparent protective outer membrane covering;
- front surface of eye (sclera)
- inner surface of eyelids
Prevents entry of microorganisms.
Lubricates eye.
What does the conjunctiva produce?
Mucus and tears.
Purpose of conjunctiva/tears and mucus
- Lubricates
- Prevents entry of microorganisms into the eyes