BIO NMDCAT

The thalamus acts as the major relay center for sensory impulses before they reach the cerebral cortex for interpretation.

The cerebral cortex contains specialized sensory areas responsible for interpreting taste, smell, vision, hearing, and touch. The brain stem does not perform conscious sensory interpretation.

The midbrain contains reflex centers responsible for visual reflexes, including pupillary constriction in response to bright light.

The medulla oblongata forms the lowest part of the brain stem and is directly connected to the spinal cord, serving as a pathway for ascending and descending nerve impulses.

Withdrawal from painful stimuli is a spinal reflex that produces a rapid response before the brain becomes consciously aware of the stimulus. The cerebrum interprets pain after the reflex has occurred.

The pons serves as a bridge between different parts of the brain, especially the cerebrum and cerebellum. It also contains respiratory centers that help regulate breathing rhythm.

The medulla oblongata contains vital autonomic centers controlling respiration, cardiac activity, and vasomotor functions. The cerebrum is involved in higher mental functions, the cerebellum coordinates movement, and the hypothalamus regulates homeostasis but does not directly control these vital reflexes.

The cerebellum coordinates voluntary muscle movements and maintains posture and balance. Damage produces ataxia, characterized by uncoordinated movements without causing paralysis.

The thalamus receives and relays almost all sensory information to the cerebral cortex. The hypothalamus regulates homeostasis, while the pons and medulla mainly conduct impulses and control autonomic functions.

The hypothalamus acts as the body's thermostat. It detects changes in temperature and initiates sweating and vasodilation to lower body temperature.

The cerebrum is the largest part of the brain and controls intelligence, memory, learning, reasoning, speech, emotions, and voluntary activities. The remaining options are functions of lower brain centers.

The cerebellum compares intended movement with actual movement and makes continuous corrections to maintain posture and balance. This function is essential during walking on uneven ground.

Hyperkalemia reduces the concentration gradient for K⁺. As a result, less K⁺ leaves the cell through leak channels, leaving more positive charge inside and shifting the resting membrane potential toward depolarization.

Irritability (excitability) is the physiological ability of a neuron or muscle cell to respond to a stimulus by generating an electrical signal. Conductivity refers to its ability to transmit that signal.

Ependymal cells are ciliated, cuboidal-to-columnar glial cells that line the fluid-filled cavities of the CNS (ventricles and central canal) and help secrete and circulate cerebrospinal fluid.

Group A fibers (like somatic motor fibers and large sensory fibers for touch and position) are the thickest, most heavily myelinated fibers in the body, providing the fastest nerve conduction velocities.

Axoaxonic synapses occur when one axon terminal synapses onto another axon terminal. They regulate (facilitate or inhibit) the amount of calcium that enters the second terminal, modulating neurotransmitter release.

Endorphins and enkephalins are endogenous opioids that bind to opioid receptors in the brain and spinal cord, powerfully blocking the transmission and perception of pain signals.

In the PNS, a bundle of axons is called a nerve. In contrast, a bundle of axons in the CNS is called a tract. A ganglion is a cluster of cell bodies in the PNS.