Free WACE Human Biology Flashcard Review

Endocrine cells release hormones into surrounding tissue fluid, from which they enter the circulation and can reach distant targets. Exocrine secretions travel through ducts to a surface or cavity. The pancreas has both functions, so naming the organ alone does not identify which kind of secretion is being described.

Target cells possess receptors that recognise the hormone and are linked to an appropriate response mechanism. Many cells may encounter the same circulating hormone without responding in the same way. A high hormone concentration cannot guarantee the expected effect if the relevant receptor or downstream signalling process is defective.

The specified structures are the hypothalamus, pituitary, thyroid, parathyroid glands, pancreas, thymus, gonads, pineal gland and adrenal glands. In a labelled body outline, use their anatomical relationships rather than assuming all endocrine glands lie near the brain. The hypothalamus is also a brain region, illustrating that nervous and endocrine organisation overlap.

Insulin generally promotes processes that lower elevated blood glucose, including uptake by responsive tissues and storage. Glucagon promotes glucose release by the liver when blood glucose is low. They act through target-cell responses rather than directly converting every glucose molecule in the blood into a different hormone.

Thyroid hormones influence metabolic activity in many tissues and therefore affect energy use and heat production. Their secretion is regulated through the hypothalamus–pituitary–thyroid pathway. Distinguish the thyroid hormone acting on body tissues from pituitary thyroid-stimulating hormone acting primarily on the thyroid gland.

Parathyroid hormone contributes to raising a low blood calcium concentration through coordinated effects involving bone and the kidneys, with an indirect effect on intestinal calcium absorption. It is produced by parathyroid tissue, not by the thyroid follicles that produce thyroid hormones. Similar names do not mean identical glands, hormones or regulated variables.

They are different regions with different hormone outputs and control pathways. The medulla releases adrenaline in responses such as acute sympathetic activation, while the cortex produces steroid hormones including aldosterone. Aldosterone influences renal sodium handling; it should not be substituted for adrenaline in an explanation of rapid cardiovascular responses.

Name the source tissue, the particular hormone and the responsive target before describing the physiological change. For example, pancreatic beta cells release insulin, which acts on appropriate liver, muscle and other target cells to influence glucose handling. Naming a gland and saying it maintains balance omits the causal steps needed to explain its effect.

Hypothalamic releasing or inhibiting hormones enter a vascular link that carries them to the anterior pituitary. They influence secretion by anterior-pituitary endocrine cells. This is a hormonal signal transported through blood vessels, not the same arrangement as hormone movement along hypothalamic axons to the posterior pituitary.

ADH is synthesised by hypothalamic neurosecretory cells and transported along their axons to the posterior pituitary, where it is stored and released into the circulation. Distinguish synthesis from release. Saying that the posterior pituitary releases ADH is appropriate; claiming that its endocrine cells manufacture ADH overlooks the hypothalamic origin.

The neural connection involves axons carrying hypothalamic products toward the posterior pituitary. The vascular connection carries regulatory hormones to anterior-pituitary cells. Both link the hypothalamus to pituitary function, but the transported material, route and target differ; a diagram should not label the portal vessels as nerves.

They can cross the lipid membrane and bind suitable intracellular receptors. The hormone–receptor interaction can influence gene expression and thereby alter cell activity. This general mechanism depends on receptor availability; lipid solubility alone does not make every cell an equivalent target or guarantee the same response in every tissue.

The hydrophobic membrane interior limits their unrestricted passage into the cell. Binding to an appropriate surface receptor initiates intracellular signalling, often involving secondary messengers. The hormone need not physically enter the cytoplasm to change cell function, and the receptor is not simply a hole through which the hormone must pass.

It is an intracellular signalling component whose activity or concentration changes after a signal reaches a membrane receptor. It helps transmit the information to processes inside the cell; cyclic AMP is one example. The extracellular hormone and the intracellular messenger are different components, and not every receptor uses one identical messenger pathway.

A signalling cascade can amplify information because one activated component can influence multiple components at the next step. This can lead to substantial changes in enzyme activity or other cellular processes from limited initial receptor activation. Amplification concerns the response pathway, not an assumption that each hormone molecule reproduces itself inside the target.

An increase in the downstream hormone or its relevant effect can reduce the upstream drive that stimulates further secretion. This opposes excessive change and helps regulate the system. Identify the feedback target and direction in the particular axis rather than treating every arrow between glands as a stimulatory signal.

The brain and spinal cord form the central nervous system. They receive, integrate and coordinate information, although different regions perform different roles. The nerves connecting them to other parts of the body belong to the peripheral nervous system; a nerve entering the spinal cord is not itself the whole spinal cord.

The peripheral nervous system comprises neural structures outside the brain and spinal cord, including nerves that connect receptors and effectors with central pathways. It carries both sensory and motor information. Peripheral does not mean only sensory, and it does not mean every peripheral response is under conscious voluntary control.

Afferent pathways carry information toward the central nervous system; efferent pathways carry commands away from it toward effectors. Use the central nervous system as the reference point. A sensory signal travelling from a foot toward the spinal cord is afferent even if its direction on a particular diagram is downward or sideways.

Somatic motor pathways act on skeletal muscle, while autonomic pathways regulate targets such as smooth muscle, cardiac muscle and glands. Somatic responses include voluntary movement but also reflex actions, so somatic is not a synonym for consciously chosen. The classification concerns the pathway and effector, not only whether the person notices the response.