Homeostasis, Coordination and Response in Humans – Review Flashcards

These question-and-answer flashcards cover key definitions, mechanisms, structures, comparisons, and examples from the lecture on homeostasis, endocrine and nervous control. Use them to quiz yourself on the fundamental concepts and details required for your exam.

What is the definition of homeostasis?

The maintenance of a relatively constant internal environment.

Why is homeostasis important for organisms?

So that metabolic processes and cell functions can occur at optimal rates.

What mechanism is mainly responsible for maintaining homeostasis?

Negative feedback mechanisms.

Define negative feedback.

A mechanism that counteracts changes in the internal environment and restores conditions toward the set norm.

In a negative-feedback loop, what detects the change in the internal environment?

Receptors (sensory cells).

In a negative-feedback loop, what term describes the change that is detected?

Stimulus.

In a negative-feedback loop, what activates to reverse the change?

Corrective mechanisms (effectors).

Give two body functions maintained by homeostasis besides temperature.

Osmoregulation (water/salt balance) and blood glucose regulation.

Define a hormone.

A chemical substance produced by a gland, carried by the blood, that alters the activity of specific target organs and is destroyed by the liver.

What is an endocrine gland?

A ductless gland that secretes hormones directly into the bloodstream.

Give an example of an exocrine gland and its secretion.

Salivary gland – secretes saliva via a duct into the buccal cavity (other acceptable: sweat gland – sweat via duct onto skin).

How does the pancreas function as both an endocrine and an exocrine gland?

Islets of Langerhans act as endocrine gland secreting insulin and glucagon into blood, while the rest of the pancreas secretes digestive enzymes via the pancreatic duct (exocrine).

What is osmoregulation?

The control of water and solute concentration in the blood to maintain constant water potential.

Which hormone is central to osmoregulation and where is it produced?

Antidiuretic hormone (ADH), produced by the hypothalamus and released by the pituitary gland.

How does ADH affect the collecting ducts of the kidney?

It increases their permeability to water, allowing more water to be reabsorbed into the blood.

What happens to ADH secretion when blood plasma becomes less negative in water potential (too dilute)?

The pituitary releases less ADH, resulting in less water reabsorption and more dilute urine.

Name the two hormones that regulate blood glucose concentration.

Insulin and glucagon.

Which pancreatic cells secrete insulin?

Beta cells in the islets of Langerhans.

Describe one effect of insulin on target organs.

It increases cell membrane permeability to glucose and stimulates conversion of excess glucose to glycogen in liver and muscles.

Which pancreatic cells secrete glucagon?

Alpha cells in the islets of Langerhans.

How does glucagon raise blood glucose?

It signals liver cells to convert stored glycogen into glucose and release it into the bloodstream.

What is diabetes mellitus in simple terms?

A persistently higher than normal blood glucose concentration due to insulin insufficiency or resistance.

Differentiate Type 1 and Type 2 diabetes in cause.

Type 1: insufficient insulin production (cells within Islets of Langerhans are destroyed by autoimmune disease). Type 2: insulin resistance of target cells (down-regulation of insulin receptors)

State one treatment for Type 1 diabetes.

Regular insulin injections to replace the missing hormone.

List any two risk factors for developing Type 2 diabetes.

Being overweight/obese, sedentary lifestyle (others: family history, high blood pressure, abnormal cholesterol, gestational diabetes).

What is sensitivity in biological terms?

The ability of an organism to detect and respond to changes in the environment.

Name the two main divisions of the human nervous system.

Central nervous system (CNS) and peripheral nervous system (PNS).

Which two structures make up the CNS?

Brain and spinal cord.

What type of neurone transmits impulses from receptors to the CNS?

Sensory neurone.

What is the function of a relay (intermediate) neurone?

To transmit impulses between sensory and motor neurones within the CNS.

What is the junction between two neurones called?

Synapse.

Which chemicals cross a synapse to transmit impulses?

Neurotransmitters.

Define an effector.

A muscle or gland that carries out a response to a nervous impulse.

State the three principal layers of human skin.

Epidermis, dermis, and fatty (subcutaneous) layer.

How does vasodilation help cool the body?

Arterioles widen, increasing blood flow near skin surface, enhancing heat loss by conduction, convection, and radiation.

What involuntary activity produces heat when body temperature falls?

Shivering – rapid muscle contractions.

Name the sense organ for temperature detection on the body surface.

Skin (thermoreceptors in the skin).

Which brain region coordinates temperature regulation?

Hypothalamus.

Identify the two fluid-filled cavities of the eye involved in pressure maintenance.

Aqueous humour (anterior cavity) and vitreous humour (posterior cavity).

Which part of the eye contains the highest concentration of cones?

Fovea of the retina.

What is the function of the choroid?

Absorbs stray light to prevent internal reflection and supplies nutrients/oxygen to the retina.

Explain accommodation for a near object.

Ciliary muscles contract, suspensory ligaments slacken, lens becomes thicker and more convex, increasing light refraction to focus on retina.

Describe the lens change when viewing a distant object.

Ciliary muscles relax, suspensory ligaments become taut, lens pulled thinner and less convex.

Define reflex action.

An immediate, automatic response to a specific stimulus without conscious control.

Which type of reflex involves the spinal cord as the control centre?

Spinal reflex (e.g., withdrawal of hand from a hot object).

Outline the pathway of a spinal reflex arc in correct order.

Receptor → sensory neurone → relay neurone (spinal cord) → motor neurone → effector.

What is the pupil reflex and its purpose?

A cranial reflex where pupil size changes with light intensity to regulate light entry and protect the retina.

Which muscles of the iris contract in bright light?

Circular muscles (radial muscles relax).

Compare the speed of nervous vs hormonal responses.

Nervous responses are usually quick; hormonal responses are generally slower.

Are hormonal responses voluntary or involuntary?

Always involuntary.

What substance carries hormones to their target organs?

Blood plasma (circulatory system).

Name one similarity between the nervous and endocrine systems in homeostasis.

Both help maintain internal conditions and coordinate body functions (other acceptable: both use chemical signals – neurotransmitters or hormones).

Why do blood glucose levels remain high after a meal?

Kidney is unable to completely reabsorb all glucose, excess is to be secreted in urine