Coordination and the human brainEdexcel A-Level Biology A: Revision notes
Section 1
Why animals need coordination
Animals must detect changes in the external and internal environment and respond. Coordination links receptors to effectors so that the whole body responds in a suitable way. Two systems do this:
- the nervous system, using action potentials along neurones and neurotransmitters at synapses
- the endocrine (hormonal) system, using hormones secreted by endocrine glands into the blood
Section 2
Nervous control
Impulses travel along neurones as action potentials, and cross synapses by neurotransmitters. Nervous control is:
- very fast, as responses can occur in milliseconds
- short-lived, as the response stops when impulses stop
- localised, as impulses reach specific effectors
Example: the pupil reflex, or the rapid increase in heart rate when startled.
Section 3
Hormonal control
A hormone is released into the blood, so it is carried to all parts of the body, but only target cells with complementary receptors respond. Hormonal control is:
- slower, as hormones must travel in the blood
- longer-lasting, because hormones persist until broken down
- widespread, as target cells in several places respond
Example: adrenaline released from the adrenal glands raises heart rate and keeps the body alert for minutes after a fright.
In compare questions, give both sides of each comparison, such as fast and short-lived against slower and long-lasting.
Do not say hormones only travel to their target. They travel everywhere in the blood but only target cells respond.
Section 4
Cerebral hemispheres and hypothalamus
The cerebral hemispheres are the two large halves of the brain. They carry out conscious thought, memory, language, and receive information from the senses. They also control voluntary movement.
The hypothalamus lies at the base of the brain. It monitors the internal environment, such as blood temperature and water content, and controls responses. It also controls the pituitary gland, so it is a link between the nervous and endocrine systems.
Section 5
Cerebellum and medulla oblongata
The cerebellum lies at the back of the brain, below the hemispheres. It coordinates movement, maintains balance and posture, using information about body position and muscle activity.
The medulla oblongata lies at the top of the spinal cord. It controls automatic (involuntary) functions such as heart rate, breathing rate and blood pressure. Damage to it can be fatal because these functions are vital.
Link each region to its function and then to the effect of damage. For example: cerebellum damaged, so movements jerky and balance poor.
That's the notes covered.
Carry on to the next subtopic.
Exam questions on Coordination and the human brain
- A 62-year-old man is admitted to hospital after a stroke that damaged part of his cerebellum. He can understand speech, think clearly and remember recent events, but his walking is unsteady and his arm movements are jerky and poorly aimed.Explain why damage to the cerebellum has caused the man's movements to be jerky and poorly aimed.2 marks
- On a hot day a runner's core body temperature begins to rise. Her skin becomes flushed and she starts to sweat. These responses are coordinated by a region at the base of her brain.Explain why the hypothalamus is described as a link between the nervous system and the endocrine system.2 marks
- A student reading quietly is startled by a loud bang. Within a second her heart rate and breathing rate increase. For several minutes afterwards she still feels alert and her heart continues to pound.Explain why the immediate response to the bang is attributed to nervous coordination but the continuing alertness is attributed to hormonal coordination.3 marks
Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).