4.5.1 Homeostasis Flashcards
4.5 Homeostasis and Response (24 cards)
What does a nerve cell contain?
Dendrites, axon, nodes, myelin, axon terminals
How does electric signals travel between nodes
It jumps from node to node
What does an abbreviated nerve cell look like
A circle with a dot (nucleus), followed by a line going out then splitting into two like a fork.
What is homeostasis?
It is the regulation of the internal conditions of a cell or organism to maintain optimum conditions for function in response to internal & external changes.
How does regulation work?
It is carried out by the nervous system (electrical) or hormonal system (chemical). All systems involve a receptor, coordinator and effector.
What are the two parts of the nervous system?
The Central Nervous System and the Peripheral Nervous System
Compare Nervous and Hormonal Systems
Nervous: Quick response, temporary response, often reversible, transmitted by neurones, communication by nerve cells, travels to specific parts of the body.
Hormonal: Slow response, permanent response, often irreversible, transmitted by blood, communication by chemicals, travels everywhere in the body but only target organs respond,
What are the steps of response in the nervous system
Stimulus > Receptor > Coordinator > Effector > Response
What are the sensory, relay and motor neurones?
The sensory neurones carry impulses from receptor to brain, while the motor neurones carry impulses from brain to effector. Relay neurones are inter-neurones that help the two neurones communicate.
What are impulses?
They are information from receptors that are passed as electrical impulses along neurones to the brain, which coordinates a response. Some responses are voluntary while some are automatic.
What is reflex action?
Reflex is a rapid automatic response to stimulus built to protect the body. The nerve pathway of a reflex is called a reflex arc
Give an example of a reflex action:
Any that makes sense to the following example
Candle > Temp Receptor in Finger > Relay neuron in spinal cord > Muscle in arm > Arm moves away from candle
What is a synapse and how does it work?
It is a junction or a gap between two neurones.
The electrical signal converts into a chemical messenger to transfer the signal into the synapse. The chemical diffuses across the gap and the messenger then binds to receptors on the postsynaptic membrane, which is then converted back into an electrical signal in the next neurone.
What does the brain consist of?
It consists of billions of interconnected relay neurones.
How do we study the brain?
MRI scans are used to study what each part of the brain does. in fMRI a task can be set to complete, and while it is being done, areas of the brain will be shown by the scanner.
(Neuroscientists also use electrodes & stimulate a small area of the brain and see what it does to the body)
What does MRI stand for?
Magnetic Resonance Imaging
How can electrically stimulating the brain be used in treatment?
Electrical stimulation of the brain can cause reduction of muscle disorders in patients with Parkinson’s disease.
What are the structures within the eye and their function?
Cornea: refracts light and protects the eye
Iris: controls how much light enters the pupil
Retina: layer of tissue at the back of the eye that contains photoreceptor cells called rods and cones.
Optic Nerve: The bundle of sensory neurones that carry impulses to the brain
Sclera: tough outer layer that extraocular muscles can attach to
Ciliary muscles: help change shape of lens in accommodation
Suspensory ligaments
How does one focus on a near object and a far object:
Near:
- ciliary muscles contract
- the suspensory ligaments loosen
- the lens is then thicker and refracts light rays strongly.
Far:
- the ciliary muscles relax
- the suspensory ligaments are pulled tight
- the lens is then pulled thin and only slightly refracts light rays.
What are the two common defects on the eye and how do they work?
Myopia: short sightedness
Hyperopia: long sightedness
- where light doesn’t get focused on the retina
How can eye defects be treated?
- Generally these defects are treated with spectacle lenses which refract the light rays so that they do focus on the retina.
- New technologies now include hard and soft contact lenses, laser surgery to change the shape of the cornea and a replacement lens in the eye.
What can body temperature be monitored/controlled by?
By the thermoregulatory centre, which contains receptors sensitive to the temperature of the blood
What happens if the body temperature is too high or too low?
HIGH: blood vessels dilate (vasodilation) and sweat is produced from the sweat glands. Both these mechanisms cause a transfer of energy from the skin to the environment
LOW: blood vessels constrict (vasoconstriction), sweating stops and skeletal muscles contract (shivering).
What is the condition called if you are too hot or cold?
HOT: Hyperthermia
COLD: Hypothermia
