B10 The Human Nervous System Flashcards
What are the two nervous systems?
- Central Nervous System (CNS)
- Peripheral Nervous System (PNS)
What does the central nervous system (CNS) consist of?
- the brain
- the spinal cord
What does the peripheral nervous system (PNS) consist of?
- nerves
What is a stimulus?
A change in enviroment which can be detected by receptors.
What are receptors?
A specialised group of cells which can detect a stimulus.
- Recpetors are found in sensory organs
What are the sensory organs?
Eyes, Ears, Tounge, Nose, Skin
What is the function of sensory neurons?
They carry electrical impulses from receptors to CNS
What does the CNS do?
The brain and spinal cord process information and co-ordinate the response
What do motor neurons do?
They carry impulses from the CNS to effectors
What are effectors?
Muscles or glands which exert the final response
What is the process for Co-ordinated Response?
Stimulus –> Receptors –> Sensory Neurons –> CNS –> Motor Neurons –> Effectors
What are some differences between sensory and motor neurons?
1) Motor neurons only have an axon where as sensory has a dendron as well
2) Cell body for sensory neuron is in the middle - don’t have dendrites
3) Cell body for motor neurons are at one end - have dendrites
4) Impulses travel towards the cell body of sensory neurons - opposite for motor
What is a reflex action?
Fast and automatic reaction to prevent further damage to your body
What is the process for Reflex Action?
Same as Co-ordinated Response but relay neurons in spinal cord replaces CNS
Why is the Reflex Action process slightly different to Co-ordinated Response process?
Impulse from sensory neuron doesn’t travel through the conscious part of the brain and it’s transferred into relay neurons in the spinal cord.
What is reaction time?
Time taken to respond to a certain or specfic stimulus
What is a way to test reaction time?
It can be tested using the ruler dropping experiment
What is the Cerebrum?
The largest part of the brain which controls higher human activities such as : memory, intelligence, languages spoken, personalitity, decision making, etc
What is the cerbellum?
It controls the voluntary muscle contractions
What is the medula?
It controls involuntary activities
What is the hypothalamus?
It’s important for homeostasis
What is the pitutary gland?
It produces hormones such as FSH, LH, ADH, TSH, GH
Three ways brain functions can be studied:
1) Case Studies
2) Electrical stimulation
3) CT and PET scanning
Why are studying brain functions difficult?
1) Brain Tissues are very sensitive and easily damaged
2) Brain tissues do not regenerate their cells
3) Case studies can have multiple factors acting on a specific area
4) Difficult to isolate areas of the brain for electrical stimulation
5) Experiments may affect emotional state of subject under test
6) Unethical as it could cause death
What is the sclera?
The outermost layer of the eye which provides protection
What is the Cornea?
A transparent layer which refracts light onto retina
What is the retina?
It has photo-receptors to detect light
- Cone cells detect colour
- Rod cells detect black and white
What is the optic nerve?
It carries electrical impules from retina to CNS
What is the iris?
Contains two types of muscle called radial and circular to control the size of the pupil
What is the lens?
It changes the shape to focus near and far objects
What is the fuction of the suspensory ligments and cililary muscles?
They changes the shape of the lens to focus near and far objects
What is the forea?
It has a lot of cone and rod cells to give the sharpest vision
How does iris reflex work?
Bright : Circular - Contract, Radial - Relax
Dark : Radial - Contract, Circular - Relax
What happens when the atmosphere is bright?
Circular muscles contract radial muscles relax - so the diameter of the pupil decreases so less light can pass through the pupil
What happens when the atmosphere is dim?
Radial muscles contracts circular muscles relax - the diameter of the pupil increases to allow in more light
What is accomodation?
The process of focusing near and far objects
How do your eyes focus on near objects?
Ciliary muscles contract which loosen the suspensory ligaments. The lens become more rounded/thicker. Light is refracted more to create the image on retina.
How do you eyes focus on far objects?
When ciliary muscles relax it causes suspensory ligaments to tighten. The lens becomes less rounded/thinner. Light is refracted less to create an image on the retina.
What is myopia?
Short sightedness - caused by too rounded or thick eye lenses, big eyeball
This means the image is created before the retina
What is hyperopia?
Long sightedness - when the eyeball is too short, wrong shape of lens
The results in the image being created behind the retina
How is myopia corrected?
A concave lens is used to diverge (spread out) the light.
or
Lazer eye surgery
How is hyperopia corrected?
A convex lens is used to converge (narrow) the light before it enters the eye.
What is colour-blindness?
A genetically passed down disease which effects the cone cells of the retina.
What is lazer eye surgery?
A beam of lazer is used to remove some tissues from cornea to make it thinner so that it refracts light less.
What is lens replacement surgery?
Lenses can be replaced by human lenses from donors or artifical kenses created by stem cells, tissue culture or nano-technology.
What is a synapse?
This is the gap between the end of one neuron and the beginning of another neuron.
How do impulses travel through a synapse?
1) At the end of a neuron there are vesicles which contain a chemical called neurotransmitters
2) When an electrical impulse reaches the end of the neuron the vesicles release the neurotransmitters into the gap
3) They difffuse and bind with the complementary recepetors on the other side of the synapse
This binding generates a new impulse
How do synapse slow down the rate of impulse transmission?
Because it takes longer for chemicals to diffuse and bind with receptors.
