nervous system Flashcards
What do animals and plants need to respond to?
Changes in their internal and external environment
Examples include changes in temperature or pH.
What are the two communication systems in mammals that transfer information for homeostasis?
- Nervous system
- Endocrine system
Which parts of the brain are involved in maintaining homeostasis?
Brain stem and spinal cord
What are the components required for a coordinated response?
- A stimulus
- A receptor
- A coordination centre
- An effector
What is the speed of information transmission through the nervous system?
Up to 100 metres per second
compare nervous and endocrine system
What is the structure of the human nervous system?
- Central nervous system (CNS) - brain and spinal cord
- Peripheral nervous system (PNS) - all of the nerves in the body
What is the pathway through the nervous system summarized as?
Stimulus → sensory neurone → relay neurone → motor neurone → effector → response
What occurs at a synapse?
Neurotransmitters transfer signals between neurones.
What is the synaptic cleft?
The small gap between two neurones at a synapse.
What are neurotransmitters?
Chemical signalling molecules used to transfer the signal between neurones at a synapse.
What does a reflex response involve?
It does not involve the conscious part of the brain.
What is a reflex arc?
The pathway of a reflex response taken by electrical impulses as they travel along neurones.
What is the role of the retina in the eye?
It contains receptor cells that detect light.
What are the two types of receptor cells in the retina?
- Rods (sensitive to light)
- Cones (detect colour)
What is the function of ciliary muscles?
To change the shape of the lens for focusing.
What happens to the lens when an object is close up?
Ciliary muscles contract, suspensory ligaments loosen, and the lens becomes fatter.
What happens to the pupil in dim light?
The pupil dilates (widens).
What is the pupil reflex in bright light?
The pupil constricts (narrows).
What is the function of the optic nerve?
It carries impulses between the eye and the brain.
What is the central nervous system linked to?
It is linked to the peripheral nervous system.
The central nervous system (CNS) consists of the brain and spinal cord.
What does the central nervous system consist of?
It contains all the nerves in the body.
Nerves are made up of long chains of neurones.
What are the three types of neurones?
- Sensory
- Relay
- Motor
How does the nervous system work to carry out a response?
A stimulus is received by sensory neurones. The sensory neurone produces an electrical signal which travels to the co-ordinator. The electrical impulse is transferred to a relay neurone, which links to a motor neurone, leading to the effector.
This describes the pathway for an involuntary coordinated response.
Why are neurotransmitters needed?
Neurones do not come into direct contact; the junction is called a synapse. The electrical impulse is converted into a chemical messenger called a neurotransmitter to cross the gap.
This process is crucial for communication between neurones.
How do electrical impulses pass from neurone to neurone?
An electrical impulse passes down the axon, triggering neurotransmitter release. They diffuse across the synaptic cleft and bind to receptors on the postsynaptic membrane to generate a new electrical impulse.
Receptors have a complementary shape to neurotransmitters, which is exploited by drugs.
What is the cornea and what is its function?
The cornea is a transparent lens that guards the eyes and refracts light as it enters the eye.
What is the iris and what is its function?
The iris is the coloured part of the eyeball that controls the shape of the pupil to regulate light entry.
What is the lens and what is its function?
The lens is a transparent shield that changes shape to focus light onto the retina, creating a sharper image.
The ciliary muscle changes the shape of the lens and is connected by suspensory ligaments.
What is the retina and what is its function?
The retina is a thin layer of tissue at the back of the eye containing receptor cells. Cone cells detect colour and rod cells detect light intensity.
The fovea is the part of the retina with the highest density of receptor cells.
What is the optic nerve and what is its function?
A sensory neurone that carries electrical impulses stimulated by light to the brain.
What is the pupil and what is its function?
A hole in the iris that lets light in.
How does the eye change when focusing on objects which are close up?
The ciliary muscles contract, suspensory ligaments loosen, and the lens becomes fatter/thicker to refract more light.
How does the eye change when focusing on objects which are far away?
The ciliary muscles relax, suspensory ligaments tighten, and the lens becomes thinner to refract less light.
How does the eye change when we are in a low-light environment?
Photoreceptors detect the change. Radial muscles contract, circular muscles relax, and the pupil dilates to allow more light in.
How does the eye change when we are in a light-abundant environment?
Photoreceptors detect the change. Radial muscles relax, circular muscles contract, and the pupil constricts to reduce light entry.
What are the four things which a co-ordinated response requires?
Coorindated responses can be to maintain homeostasis or to voluntarily coordinate a response such as moving
a
A stimulus (e.g. change in body temperature)
A receptor (e.g. receptor cells)
A co-ordination centre (e.g. brain or spinal chord which receives and processes information from receptors
An effector (e.g. muscle shivering) which brings about the response
