Homeostatis And Response Flashcards
How can the cells in the body survive?
Within narrow physical and chemical limits. They require a constant temperature and PH as well as a constant supply of food and water.
How does the body maintain a constant temperature and PH?
The body requires control systems that constantly monitor and adjust the composition of the blood and tissue.
What do the control systems in the body include?
Receptors which sense changes and effectors that bring about changes.
What is homeostasis?
Homeostasis is the regulation of the internal conditions of a cell or organism to maintain optimum conditions for function in response to internal and external changes.
Why is homeostasis important?
It keeps conditions constant for enzyme action and cell functions.
What does homeostasis include the control of?
Blood glucose concentration
Body temperature
Water and ion levels
What does this automatic control system (homeostasis) involve?
Nervous or chemical responses.
What do all control systems include?
- Cells called receptors, which detect stimuli (changes in the environment).
- Coordination centres (such as the brain, spinal cord and pancreas) that receive and process information from receptors.
- effectors, muscles or glands, which bring about responses which restore optimum levels.
What temperature should the human body be kept around?
37 degrees
Why does the body have a temperature that it should be kept at?
So there is an optimum temperature for enzymes to work.
What does the thermoregulatory centre in the brain do?
- Monitors and controls body temperature
- Has receptors that monitor the temperature of the blood flowing through the brain
- Receives information (impulses) from temperature receptors in the skin.
What happens if body temperature is too high?
- Vasodilation, blood vessels widen, directing more blood to the surface of the skin.
- More sweat is produced from sweat glands and evaporates
- Hair and hair erector muscles are relaxed.
What do all the mechanisms that happens to the body when you’re too hot cause?
A transfer of energy from the skin to the environment.
What happens is body temperature is too low?
- Vasoconstriction, blood vessels narrow directing blood away from the surface of the skin.
- Sweating stops
- Skeletal muscles uncontrollably contract and relax quickly (shiver), which transfers more heat to the blood.
- Hair and hair erector muscles stand on end to trap a layer of air.
What does the human nervous system enable humans to do?
To react to their surroundings and to coordinate their behaviour.
How is information passed along the nervous system?
Information from receptors passes along cells (neurones) as electrical impulses to the central nervous system (CNS). The CNS coordinates the response of effectors which may be muscles contracting or glands secreting hormones.
What is the CNS?
The brain and the spinal cord.
What are reflex actions and why?
Reflex actions are automatic and rapid so that they can protect the brain.
How do reflex actions happen?
- Pain stimulus is detected by receptors.
- Impulses from the receptor pass along a sensory neurone to the CNS.
- An impulse passes through a relay neurone.
- A motor neurone carries an impulse to the effector.
- The effector (usually a muscles) responds e.g. to withdraw a limb from a source of pain.
In a reflex action in which order is the message passes along the nervous system?
Stimulus - Receptor - Coordinator - effector - response
Why does a reflex arc not include the conscious part of the brain?
So we cannot override the response.
What is the position of neurones like?
They are not directly connected to each other.
How do neurones communicate with each other?
Via synapses (gaps between neurones).
What happens when an electrical impulse reaches a synapse?
A chemical is released that diffuses across the gap between the two neurones. This causes an electrical impulse to be generated in the second neurone.
What does the brain control and what is it made up of?
The brain controls complex behaviour. It is made up of billions of interconnected neurones and has differ t regions that carry out different functions.
What does the cerebral cortex do?
- Makes up 3/4 of the brain’s volume
- Mase up of neurones and nerve fibres that transfer information
- Responsible for learning, reasoning, speech, sight and hearing.
- Concerned with consciousness, intelligence, memory and language
What does the cerebellum do?
- Consists of nerve cells and nerve fibres.
- Coordinated muscle movement, controlling muscular activity and balance
- Responsible for carrying signals to other parts of the brain and spinal cord.
What does the hypothalamus in the brain do?
Releases hormones, controls temperature.
What does the medulla do?
- Creates sensory pathways between spinal cord and brain.
- Controls unconscious activities e.g. heartbeat and breathing.
What does the pituitary gland in the brain do?
- Responsible for producing and regulating neuro chemicals
- Produces hormones which control the body via homeostasis
What are the three main parts of the brain?
The cerebellum, cerebral cortex and the medulla
How are neuroscientists able to map the regions of the brain to particular functions?
- Studying patients with brain damage, looking at the areas affected and the change in person.
- Electrically stimulating parts of the brain, surgeons cut out part of skull and use electrical signals to stimulate parts of the brain.
- MRI scans can light up when an area is stimulated due to activity or does not light up due to damage.
Why is investigating and treating brain disorders very difficult?
Because of the complexity and delicacy of the brain. Hey
What is the eye?
A sense organ containing receptors sensitive to light intensity and colour.
What does the retina do?
The retina contains receptor cells that are sensitive to the brightness and colour of light.
What does the optic nerve do?
Carries impulses from the retina to the brain.
What does the sclera do?
Forms a tough outer layer with a transparent region at the front called the cornea.
What does the iris do?
Controls the side of the pupil and the amount of light reaching the retina.
What do the ciliary muscles and the suspenseful ligaments do?
They can change the shape of the lens to focus light onto the retina.
What are the parts of the eye?
Retina, optic nerves, sclera, cornea, iris, ciliary muscles, suspensory ligaments
What is accommodation?
The process of changing the shape of lens to focus on near objects.
How does the eye focus on near objects?
- The ciliary muscles contract
- The suspensory ligament loosen
- The lens is then thicker and refracts light rays strongly
How does the eye focus on distant objects?
- The ciliary muscles relax
- The suspensory muscles are pulled tight
- The lens is then pulled thin and only slightly refracts light rays much
What are the two common defects of the eyes?
Myopia (short sightedness) and hyperopia (long sightedness) in which light rays do not focus on the retina.
How are defects of the eye generally treated?
With spectacle lenses which refract the light rays so that they do focus on the retina.
What do new technologies to correct eye defects include?
Hard and soft contact lenses, laser surgery go change the shape of the cornea and a replacement lens in the eye.
Why are people short sighted?
In short sighted people, light rays meet in front of the retina and so the image is blurred.
How is myopia (short sightedness) corrected?
Using a diverging/ concave lens to spread light rays out before they hit the cornea do they can focus on the retina.
Why are people long sighted?
Light rays meet behind the retina and so the image is blurred, eye cannot focus on near by images.
How is hyperopia (long sightedness) corrected?
Use a converging lens to narrow beams of light rays before they hit they hit the cornea so they can focus on the retina.
What are contact lenses?
Lenses placed on the eye
What are replacement lenses?
The natural lens is left in place but a contact lens is permanently implanted or natural lens is removed and placed by an artificial lens.
What is laser eye surgery?
Shape of cornea is changed to cause light to be focussed closer/ further away, this is only available to adults.
How does the endocrine system work?
It is composed of glands which secrete chemicals called hormones directly into the blood stream. The blood carries the hormone to a target organ where it produces an effect.
What is the endocrine system like compared to the nervous system?
Compared to the nervous system the effects are slower but act for longer.
What are the parts of the endocrine system?
Pituitary gland (in the brain) Pancreas Thyroid (in the throat) Adrenal gland (above pancreas) Ovary Testes
What is the pituitary gland?
The pituitary gland in the brain is a ‘master gland’ which secretes several hormones into the blood in response to body conditions. These hormones in turn act on other glands to stimulate other hormones to be released to bring about effects.
What does the pancreas do?
Produces the hormone insulin which is responsible for controlling the level of glucose in the body.
What does the thyroid gland do?
Releases a hormone called thyroxine that controls the body’s metabolism (the way the body uses energy) it also stimulates and controls growth in young animals. Thyroxine’s controlled by negative feedback.
What does the adrenal gland do?
The adrenal gland produces adrenaline in times of fear of stress which increases the heart rate boosting the delivery of oxygen and glucose to the brain and muscles. Adrenaline prepares the body for ‘flight or fight’.
