9 Coordination and Response Flashcards
Describe a nerve impulse
An electrical signal that passes along nerve cells called neurons.
Describe the human nervous system
Consists of
- The central nervous system (brain and spinal cord) which processes nervous impulses from body and coordinates any response.
- Specialised receptor organs (sense organs such as eye and ear) that contain receptor cells which sense stimuli.
- Nerves (large bundles of many neurons) of the peripheral nervous system that connect the central nervous system to other parts of the body.
- Specialised effectors which produce the response to the stimulus such as contraction of muscles and secretion of hormones.
Describe a reflex arc
A reflex arc is the pathway that impulses travel along during a reflex.
Stimulus detected by a receptor, sensory neuron sends electrical impulses to the spinal cord. Electrical is passed on to relay neuron in the spinal cord. Relay neuron connects to motor neuron and passes impulse on. Motor neuron carries impulse to an effector and a response is made.
Describe a reflex action
A means of automatically and rapidly integrating and coordinating stimuli with the responses of effectors (muscles and glands).
Difference between Voluntary response and Involuntary response
A voluntary response is one where you make a conscious decisions to carry out a particular action therefore it starts with your brain. An involuntary (or reflex) response does not involve the brain as a coordinator of the reaction and you are not aware until after it is carried out. They are usually essential to basic survival and are rapid.
Role of Cornea
Refracts light.
Role of Iris
Controls how much light enters pupil.
Role of Lens
Focuses light onto retina.
Role of Retina
Contains light receptors, some sensitive to light of different colors.
Role of Optic nerve
Carries impulses to the brain.
Explain the pupil reflex
A reflex action carried out to protect the retina from damage in bright light and protect us from not seeing objects in dim light. In dim light the pupil dilates (widens) in order to allow as much light into the eye as possible. In bright light the pupil constricts (narrows) in order to prevent too much light entering eye and damaging the retina.
Define Accommodation
The function of the eye in focusing on near and distant objects.
The lens is elastic and its shape can be changed when the suspensory ligaments attached to it become tight or loose.
Explain accomodation in the eye to near objects
When an object is close up the ciliary muscles contract. This causes the suspensory ligaments to loosen, stopping them from pulling on the lens which allows it to become fatter. Light is refracted more.
Explain accomodation in the eye to distant objects
When an object is far away the ciliary muscles relax. This causes the suspensory ligaments to tighten, making them pull on the lens causing it to become thinner. Light is refracted less.
Describe Hormone
A chemical substance, produced by an endocrine gland, carried by the blood, which alters the activity of one or more specific target organs.
Describe Adrenaline
The hormone secreted in the adrenal gland during ‘fight or flight’ situation and its effects are an increased pulse rate, depth of breathing, and dilates pupils for better vision.
Which organ regulates hormones?
The liver. Breaks down or transform any in excess.
How are hormones transported around the body?
Endocrine glands have a good blood supply as they need to get the hormones into the bloodstream as soon as possible so they can reach the target organs and bring a response. The hormones only affect cells with target receptors they can bind to.
Describe Insulin
A hormone secreted in the pancreas to lower blood glucose levels. Causes excess glucose in the blood to be taken up by the muscles and liver and converted into glycogen for storage.
Describe Testosterone
A hormone secreted in the testes. It is the main sex hormone in males, for the development of the secondary sexual characteristics in males.
Describe Estrogen
A hormone secreted in the ovaries. It is the main sex hormone in females, for the development of secondary sexual characteristics in females and controls menstrual cycle.
Differences between nervous and hormonal system.
Nervous system:
Made up of: nerves, brain and spinal cord.
Type of message: electrical impulse.
Speed of transmission: very fast.
Length of effect: short - until nerve impulses stop.
Endocrine system:
Made up of: glands.
Type of message: chemical hormones.
Speed of transmission: slower.
Length of effect: longer - until hormone is broken down.
Define Homeostasis
The maintenance of a constant internal environment.
Role of Insulin in homeostasis
Insulin is secreted into the blood at times when glucose levels are high. This is most often directly after a meal. The kidneys can only cope with a certain level of glucose in the blood. If it is too high, insulin is released and converts excess glucose into glycogen to decrease blood glucose concentration.
