B10 - The Human Nervous System Flashcards
Define homeostasis.
kpng condtns. inside cell or body @ optimum levels
What is a stimulus?
△ in envrnmnt
What do receptor cells do?
detects △ in envrnmnt (can be internal or external)
Give 3 examples of a coordination centre.
brain, spinal cord & pancreas
What does the coordination centre do?
processes info from receptor cells & sends instrctns -> effectors
Define effector.
muscles eg.contracts or glands eg.secretes hormones that carries out response
What is the typical order for automatic control system?
stimuli -> receptor -> coordination centre (CNS) -> effector -> response!
What is the CNS? what does it consist of?
central nervous system - brain & spinal cord
How do parts of the reflex arc send electrical impulses?
down neurones
What would detect the heat if you touched a hot object?
temp. receptors in skin
After receptors detecting that you have touched a hot object, what happens?
electrical impulses go from receptor, along sensory neurone -> CNS
At the end of any neurone, what is there? What happens there?
synapse = which releases neurotransmitter that diffuses to next neurone in CNS & triggers electrical impulse
Why does the temperature of your body need to be controlled?
too ↑ & enzymes dntr
too ↓ & enzymes work too slowly
Where are temperature receptors found?
skin & brain
Which coordination centre maintains temperature?
brain
How do the effectors respond to a temperature change?
muscles - shiver
glands - sweat
Why do the water and ion levels of plants need to be controlled?
too ↑ & H2O leaves cells by osmosis
too ↓ & H2O enters cells by osmosis & cells burst
Where are water and ion level receptors found?
brain
Which coordination centre maintains water and ion levels?
brain
How do the effectors respond to a change in water & ion levels?
glands - release hormones change how dilute urine is
Why does the blood sugar of the human body need to be controlled?
too ↑ & causes circulation probs.
too ↓ & can’t respire
Where are the blood sugar receptors found?
pancreas
What is the coordination centre that maintains blood sugar levels?
pancreas
How do the effectors respond to low blood sugar levels?
glands - release hormones control blood sugar levels
What is the order for the reflex arc?
sensory neurone -> relay neurone -> motor neurone
Define synapse.
junction between neurones
What happens at the synapse in the reflex arc?
- neurotransmitter released at end of snsry neurone
- neurotransmitter diffuses across to rly neurone in CNS
- this triggers electrical impulse
- elctrcl impulse passes along rly neurone & reaches next synapse
What does the cerebal cortex in the brain do?
controls consciousness, intelligence, memory & language
What does the pituitary gland do?
produces many different hormones to coordinate & control body systems
What does the cerebellum do?
controls coordinating muscular activity & balance
What are 4 things that will affect reaction time?
alcohol, caffeine, biological sex, fatigue
What 3 reasons explain why it is difficult to study the brain & treat brain disease/damage?
- brain = protected by skull so tricky to access
- structures of brain = extremely complex
- brain = extremely delicate & easy -> damage
What are 3 ways that scientists investigate the brain?
- see where damage has tkn place & link to its function
- elctrclly stimulate parts of brain & observe effects on person’s behaviour
- use MRI scanning -> see which parts of brain are most active during activities
What is the cornea’s function?
Refracts light - it bends as it enters the eye
What is the lens’ function?
Further refracts the light to focus it onto the retina
What is the retina’s function?
bck of eye - contains the light receptors which send elctrcl impulses -> optic nerve in brain
What is the optic nerve’s function?
Carries the electrical impulses between the brain & the eye
What is the scelra’s function?
tough white outer layer that protects eye
What is the iris’ function?
controls how much light enters eye
- dark room= little light enters, muscle contracts & pupil size increases
- bright room= lots of light enters, muscles relax & pupil size decreases
What is the pupil’s function?
Small hole at centre of iris through which light enters eye
What is the suspensory ligaments function?
connects ciliary muscle -> lens & holds lens in place
What is the ciliary muscle’s function?
change thickness of lens by cntrctng or rlxng
Define accomodation.
ability -> change shape of lens -> focus on nar or distant objects
What are the cilary muscles?
muscles connctd -> lens by sspnsry lgmnts
How does the eye focus on a near object?
- ciliary muscles contrct
- sspnsry lgmnts loosen
- lens is now thicker & rfrcts light rays more strongly
How does the eye focus on a distant object?
- ciliary muscles contract
- sspnsry lgmnts are pulled tight
- lens is now pulled think & only slightly refracts light rays
