Most Repeated MDCAT Biology: Coordination and Control MCQs

Explanation

The autonomic nervous system does not directly control thought processes. Thought is primarily regulated by the central nervous system, which includes the brain and spinal cord. While the autonomic nervous system can be influenced by certain thought patterns, such as stress or relaxation, it does not directly control the generation or content of thoughts.

Explanation

A feedback mechanism is a loop system wherein the system responds to a perturbation. The response may be in the same direction (as in positive feedback) or in the opposite direction (as in negative feedback). An example of positive feedback is uterine contractions during childbirth. The hormone oxytocin, made by the endocrine system, stimulates the contraction of the uterus. This produces the pain sensed by the nervous system. In response, more oxytocin is released which in turn stimulates the contractions even more.

Explanation

The amygdala controls the sensation of pleasure, punishment, or sexual arousal. The hippocampus has a major role in learning and memory. The hypothalamus is considered to be a link structure between the nervous and the endocrine system; its main function is to maintain the homeostasis of the body. The thalamus has several functions, such as relaying of sensory signals, including motor signals, to the cerebral cortex and the regulation of consciousness, sleep, and alertness.

Explanation

Negative feedback mechanisms are a characteristic of Class Mammalia. A negative feedback mechanism is a regulatory process where the response to a stimulus reduces or stops the stimulus, maintaining stability or homeostasis. This mechanism works by counteracting a change to return a system to its set point, similar to how a thermostat turns off the furnace once the room reaches the desired temperature. Examples include the body regulating blood glucose, body temperature, and the secretion of hormones.

Explanation

The arachnoid mater is the middle layer of the meninges. It is a thin and delicate membrane that lies between the dura mater (outer layer) and pia mater (inner layer). The arachnoid mater has a web-like appearance and is named after its resemblance to a spider's web.

Explanation

Glucagon is a hormone released by the pancreas, which helps maintain blood sugar levels. It does this by converting glycogen into glucose, thus increasing blood sugar.

Explanation

Antidiuretic hormone (ADH) is produced in the area of the brain called the hypothalamus. This hormone is stored in and released by the posterior pituitary gland. ADH controls how our body releases and conserves water.

Explanation

The main difference between dendrites and axons lies in their terminal portions. Dendrites have numerous branches at their terminals, which receive signals from other neurons and transmit them towards the cell body. Axons, on the other hand, have a single branch called the axon terminal, which transmits signals away from the cell body to other neurons or effector cells.

Explanation

During the non-conducting state (resting state) of a neuron, the neuronal membrane is primarily permeable to the efflux of potassium ions (K⁺). This permeability is due to the presence of potassium channels that allow K⁺ to flow out of the cell, contributing to the resting membrane potential, which is typically around -70 mV. The efflux of K⁺ ions occurs because of their higher concentration inside the neuron compared to the outside, leading to a net outward movement and a negative charge inside the neuron.

Explanation

Basal metabolic rate is increased by normal or over-secretion of the thyroid gland. Glycogen is converted into glucose in the process known as glycogenolysis under the action of the enzyme glucagon which gets secreted when energy is deficient. The pancreas secretes glucagon, which promotes the conversion of glycogen to glucose. Na+ absorption occurs in the distal nephron. This process is regulated by hormones such as aldosterone and antidiuretic hormone (ADH). (Right answer): If your entire thyroid is removed, your body can no longer make thyroid hormones. Hypothyroidism is a common condition where the thyroid doesn’t create and release enough thyroid hormone into your bloodstream.

Explanation

In humans, prolactin is produced both in the front portion of the pituitary gland (anterior pituitary gland) and in a range of sites elsewhere in the body. Lactotroph cells in the pituitary gland produce prolactin, where it is stored and then released into the bloodstream.

Explanation

A sensory neuron is a nerve cell that detects and responds to external signals via receptors and converts this information into electrical impulses. These electrical responses are then transmitted to interneurons via sensory neurons, where information is processed and signals are sent to the effectors through motor neurons.

Explanation

The adrenal glands are often referred to as the "glands of emergency" because they play a crucial role in the body's stress response. These glands produce hormones such as adrenaline and cortisol, which prepare the body to respond to stressful situations by increasing heart rate, raising blood pressure, and mobilizing energy resources.

Explanation

The correct sequence of events at the neuromuscular junction is as follows:Nerve impulse triggers the release of Acetylcholine (V) from the presynaptic neuron.Acetylcholine binds to receptors, generating an End Plate Potential, leading to an Action Potential (W) in the muscle fiber.The Action Potential triggers the release of Calcium ions (X) from the sarcoplasmic reticulum.Calcium ions bind to regulatory proteins, allowing the formation of Actomyosin (Y) cross-bridges, leading to muscle contraction.

Explanation

Action potential is a temporary localized reversal of the polarity of the neurolemma, which occurs when the neurolemma is stimulated (e.g.electric shock, touch, sound, vibrations, etc). During the action potential, the polarity of the neurolemma first changes to +40mv (depolarization) and then restores to -65mv again (i.e., repolarization). This action is extremely rapid as it occurs only in a few milliseconds. to happen. Hence, option B is correct.

Explanation

The hippocampus is a complex brain structure, curved like a seahorse, located deep in the temporal lobe, that is critical for learning and memory, especially for converting short-term memories into long-term ones.

Explanation

Option A: Synapse: The region where the impulse moves from one neuron to another is called a synapse. Option B: Monosynaptic: A reflex usually involves two neurons, a sensory neuron and a motor neuron. The pathway of such transmission is the reflex arc. In this case, since only one synapse is involved, such a reflex is called monosynaptic. Option C: Reflex arc: A reflex arc is the neural pathway that mediates a reflex action, allowing for a rapid, involuntary response to a stimulus without conscious thought from the brain. This pathway typically involves a sensory receptor, a sensory neuron, a relay neuron (in more complex arcs), a motor neuron, and an effector (like a muscle or gland).

Explanation

Calcium ions cause the vesicles containing neurotransmitters to fuse with the axon terminals and release the neurotransmitter into the synaptic cleft. The neurotransmitters bind to the receptors on the postsynaptic membrane, which generate an action potential in the postsynaptic cell. Hence, option C is correct.

Explanation

Dopamine, along with acetylcholine, norepinephrine (noradrenaline), glycine, GABA, serotonin, etc., acts as a neurotransmitter. Dopamine is a neurotransmitter and hormone that plays a crucial role in movement, motivation, pleasure, and the brain's reward system. Hence, option B is correct.

Explanation

The cerebrum is the largest part of the brain, divided into two hemispheres that control high-level functions like conscious thought, voluntary movement, sensory processing, memory, and emotions. It is divided into four lobes (frontal, parietal, temporal, and occipital) and is responsible for conscious actions, processing what the senses pick up, and complex cognitive processes like language and reasoning.

Explanation

GABA, or gamma-aminobutyric acid, is the primary inhibitory neurotransmitter in the central nervous system, responsible for reducing neuronal excitability and creating a calming effect by blocking nerve signals.

Explanation

Language comprehension is a function of the cerebrum.Cerebellum coordinates and controls rapid muscular activities such as running, typing etc. Although it does not initiate such voluntary movements, it is an important centre for coordinating movements and for controlling posture and balance. Cerebellum’s function is almost exclusively motor; but it is also implicated in some forms of learning.

Explanation

The hypothalamus lies at the base of the thalamus. It provides an anatomical connection between the nervous and endocrine systems through its relationship to the pituitary gland. The hypothalamus is a thermoregulatory centre. Hence, it is called the “thermostat” of the body. It keeps body temperature at roughly 37°C by means of a complex thermostat system. Any localised injury to the hypothalamus will, hence, disrupt the regulation of body temperature.

Explanation

Peripheral motor nerves carry motor impulses from the spinal cord to voluntary muscles. The destruction of the cells of the anterior horn of the spinal cord will result in the loss of voluntary motor impulses. This is because the cells of the anterior horn (also called the anterior gray column), which is the front column of gray matter in the spinal cord, contain motor neurons that innervate the axillary muscles.

Explanation

Adrenaline triggers the body's fight-or-flight response. This reaction causes air passages to dilate to provide the muscles with the oxygen they need to either fight danger or flee. Adrenaline also triggers the blood vessels to contract to re-direct blood toward major muscle groups, including the heart and lungs.