2.7: Sense Organs, Homeostasis, and Body Systems

Comprehensive vocabulary flashcards covering sense organs, homeostasis mechanisms, the nervous system structure, and the endocrine system based on the Topic 2.7 review notes.

Sense organs

Specialised structures that detect stimuli (such as light, sound, touch, taste and smell) in your environment.

Receptors

Chemical structures that receive and convert signals in the body; including thermoreceptors, mechanoreceptors, chemoreceptors, photoreceptors and pain receptors.

Thermoreceptors

Special cells located in your skin, part of your brain and body core that are sensitive to temperature.

Mechanoreceptors

Special cells within the skin, inner ear and skeletal muscles that are sensitive to touch, pressure and motion.

Chemoreceptors

Special cells within a sense organ that are sensitive to particular chemicals.

Photoreceptor

A special cell located in your eye that is stimulated by light.

Pain receptors

Special cells located throughout the body (except the brain) that send nerve signals to the brain and spinal cord in the presence of damaged or potentially damaged cells.

Homeostasis

The maintenance by an organism of a constant internal environment (for example, blood glucose level, pH, body temperature).

Stimulus–response model

A system in which a change (stimulus) is detected by receptors leading to a response, which acts to alter and return the variance to normal.

Negative feedback

A homeostatic mechanism that returns a stimulus back within its normal range (response is in an opposite direction to the stimulus).

Positive feedback

Occurs when the response is in the same direction as the change in stimulus, such as the release of oxytocin during childbirth.

Central nervous system (CNS)

The part of the nervous system composed of the brain and spinal cord.

Peripheral nervous system (PNS)

The part of the nervous system containing nerves (neurons) that connect the central nervous system to the rest of the body.

Sensory neurons

A nerve cell in the sensory organs that conducts a nerve impulse from receptors to the central nervous system.

Interneuron

A nerve cell that conducts a nerve impulse within the central nervous system, providing a link between sensory and motor neurons.

Motor neuron

A nerve cell that conducts a nerve impulse from the central nervous system to the effector, such as a muscle or gland.

Synapse

The gap between adjoining neurons where neurotransmitters travel.

Neurotransmitters

Signalling molecules released from the axon terminals into the synapse between nerve cells (neurons).

Dendrite

Structure that relays information towards the cell body of a neuron.

Cell body

Part of a neuron that contains the nucleus.

Axon

Long structure within a neuron through which the nervous impulse travels from the dendrite and the cell body.

Myelin

A fatty, white substance that encases the axons of neurons.

Reflex arc

A quick response to a stimulus that does not involve the brain; the message travels from receptor to sensory neuron to interneuron in the spinal cord then directly via the motor neuron to the effector.

Cerebrum

The largest part of the brain responsible for higher order thinking, controlling speech, conscious thought and voluntary actions.

Cerebellum

The part of the brain that controls balance and muscle action.

Reticular formation

A network of neurons that controls the amount of information that flows into and out of the brain, regulating alertness, motivation, and movement.

Endocrine system

The body system composed of different glands that secrete signalling molecules (hormones) into the blood for internal communication, regulation and homeostasis.

Hormone

A signalling molecule that is produced in specialised cells and travels in blood to act on target cells to cause a specific response.

Insulin

Hormone, produced by the pancreas, that reduces blood glucose levels.

Glucagon

A hormone, produced by the pancreas, which increases blood glucose levels.

Hyperglycaemia

Blood glucose levels above the normal range.

Hypoglycaemia

Blood glucose levels below the normal range.

Follicle-stimulating hormone (FSH)

Regulates the development, growth and reproductive processes of the body.

Luteinising hormone (LH)

Hormone produced by the anterior pituitary gland that initiates ovulation and progesterone production in females and testosterone production in males.

Adrenaline

A hormone secreted in response to stressful stimuli, which readies your body for the fight-or-flight response.

Cochlea

The snail-shaped part of the inner ear in which receptors are stimulated.

Ossicles

A set of three tiny bones that send vibrations from the eardrum to the inner ear.

Cornea

The curved, clear outer covering of your eye.

Iris

Coloured part of the eye that opens and closes the pupil to control the amount of light that enters the eye.

Retina

Curved surface at the back of the eye containing photoreceptors.

Rods

Photoreceptors located in the retina that respond to low levels of light and allow viewing in black and white in dim light.

Cones

Photoreceptors located in the retina that respond to red, green or blue light.

Autonomic nervous system

Part of the PNS that controls involuntary movement, such as breathing or heartbeat.

Somatic nervous system

Part of the PNS that controls voluntary movement, such as walking.

Hippocampus

Part of the brain with a key role in consolidating learning and converting information from working memory to long-term storage.

Motor neuron disease

A medical condition that progressively destroys motor neurons, resulting in progressive paralysis but leaving the brain and sense organs unaffected.