CIE IGCSE Biology: Coordination, Response & Homeostasis

The human nervous system consists of the central nervous system (CNS), which comprises the brain and spinal cord, and the __________ nervous system, which includes all the nerves in the body.

peripheral

Information is transmitted through the nervous system as electrical signals called nerve impulses, which travel along nerve cells known as neurones, while a bundle of neurones is termed a __________.

nerve

In this diagram of neurone types, the neurone characterised by a long axon with a cell body branching off the middle is a __________ neurone.

sensory

On a neurone, short, branched extensions of the cytoplasm called __________ carry impulses toward the cell body, while the axon carries impulses away from it.

dendrites

The axon is insulated by a fatty sheath with small uninsulated sections called __________, which allow impulses to jump rapidly from one to the next.

nodes

Unlike voluntary responses which require a conscious decision and start in the brain, reflex actions are fast, protective, and __________.

automatic

According to the reflex pathway flowchart, an impulse moves from the sensory neurone to the __________ neurone before passing to the motor neurone.

relay

The junction between two adjacent neurones across which nerve impulses are chemically transmitted is known as a __________.

synapse

As shown in the synapse diagram, vesicles release chemical messengers called neurotransmitters that diffuse across the synaptic cleft and bind to receptor molecules located on the __________ membrane.

postsynaptic

In the structure of the human eye, the transparent front layer that refracts light entering the eye is the __________.

cornea

The area of the retina that contains the highest concentration of cone cells and forms sharp, colour images is called the __________.

fovea

In dim light, the pupil dilates to let in more light because the circular muscles of the iris relax while the radial muscles __________.

contract

In bright light, the pupil constricts to protect the retina because the radial muscles relax while the circular muscles __________.

contract

When the eye accommodates to focus on a near object, the ciliary muscles contract, the suspensory ligaments loosen, and the lens becomes __________.

fatter

When the eye focuses on a distant object, the ciliary muscles relax, the suspensory ligaments tighten, and the lens becomes __________.

thinner

In the retina, __________ cells are sensitive to low levels of light for night vision, whereas cone cells allow colour vision.

rod

Situated at the base of the brain, the endocrine gland often referred to as the 'master gland' is the __________ gland.

pituitary

Hormones are chemical substances secreted by endocrine glands directly into the blood __________, which carries them to specific target organs.

plasma

The 'fight or flight' hormone released by the adrenal glands that increases pulse rate, breathing rate, and blood glucose concentration is __________.

adrenaline

Homeostasis is defined as the maintenance of a constant __________ environment within the body.

internal

When blood glucose levels rise above the set point, the pancreas releases insulin to stimulate muscle and liver cells to store excess glucose as __________.

glycogen