B10 The human nervous system Flashcards
What is homeostasis?
The process by which your body maintains a constant internal environment
Why is homeostasis important?
To maintain optimal conditions for enzyme actions
What does homeostasis rely on?
Automatic control systems such as your nervous system, hormones and body organs
What are the internal conditions that are controlled? (3)
Water content, body temperature and blood glucose concentration
How does water leave the body? (3)
Respiration, sweat and urine
What is the core body temperature?
37 degrees celsius
What controls the level of glucose in your blood?
The pancreas
What is the energy source for cells?
Glucose
What do receptor cells do?
Detect stimuli in the external or internal environment
What does the coordination centre include? (3)
The brain, spinal cord and pancreas
What are effectors and what do they do?
Usually muscles or glands that bring responses to stimulus
Where are receptor cells found?
In sense organs
What two things make up the central nervous system?
The brain and spinal cord
What are nerve cells called?
Neurones
What is a bundle of neurones called?
Nerves
What do sensory neurones do?
Carry impulses from receptors to the CNS
What do motor neurones do?
Carry impulses from CNS to effectors, which then respond to the impulses
How do muscles respond to impulses?
Contracting
How do glands respond to impulses?
Secreting chemicals
What are the main steps involved in reflexes?
A receptor detects a stimulus > a sensory neurone transmits the impulse to the CNS > a relay neurone in the CNS passes the impulse on > a motor neurone is stimulated > motor neurone passes the impulse to an effector > action is taken
What is the gap between two neurones called?
Synapses
What is the sequence from a receptor to an effector called?
A reflex arc
What does the cerebral cortex control?
Consciousness, intelligence, memory and language
What does the cerebellum control?
Coordination of muscular activity
What does the medulla control?
Unconscious activities, such as controlling heartbeat and breathing
What does the pituitary gland do?
Produces hormones
How have scientist been able to map out the brain?
By studying patients with brain damage, electrically stimulating parts of the brain, using MRI
What is the sclera?
Tough, white outer layer that prevents damage to the eye
What is the cornea?
Transparent area in front of sclera that lets light into the eye
What do the muscles of the iris do?
Contract and relax to control the size of the pupil
How do the muscles of the iris respond to bright light?
The circular muscles contract, radial muscles relax and pupil constricts, getting smaller
How do the muscles of the iris respond to dim light?
Circular muscles relax, radial muscles contract and pupil dilates
What does the lens do?
Clear disc held in place by suspensory ligaments and the ciliary muscles, changes direction of the light so that the image is focused
What does the optic nerve do?
Carries impulses from the retina to the brain
What is accommodation?
The process of changing the shape of the lens to focus on objects
How do the lens change shape to focus on close objects?
The ciliary muscles contract, the suspensory ligaments loosen and the lens becomes thicker so it can refract light rays strongly
How do the lens change shape to focus on distant objects?
The ciliary muscles relax, the suspensory ligaments are pulled tight and the lens in pulled so it only refracts light rays slightly
What is myopia?
Short sightedness
What is hyperopia?
Long sightedness
How can slight defects in the eye be treated?
Spectacle lenses to refract light rights, laser surgery, lens replacement
