Organization and Sensory Physiology of the Nervous System Flashcards

Front

Nervous System Divisions

Back

The nervous system divides into the Central Nervous System (CNS) and the Peripheral Nervous System (PNS). The CNS includes the brain and spinal cord, while the PNS comprises cranial and spinal nerves, ganglia, sensory receptors, and enteric plexuses.

Front

CNS Functions

Back

The CNS integrates sensory information and generates responses to maintain homeostasis and behavior. It processes complex functions like consciousness, memory, and voluntary movement.

Front

PNS Functions

Back

The PNS provides communication between the CNS and the rest of the body via afferent (sensory) and efferent (motor) pathways. It conveys sensory input to the CNS and carries motor commands to muscles and glands.

Front

Neuron Types

Back

Neurons are classified as sensory (afferent), motor (efferent), and interneurons. Sensory neurons carry information to the CNS, motor neurons transmit responses to effectors, and interneurons connect neurons within the CNS.

Front

Reflex Definition

Back

A reflex is an automatic response to a stimulus mediated by a reflex arc that typically involves a receptor, sensory neuron, integration center in the CNS, motor neuron, and effector. Reflexes help regulate homeostasis and provide rapid protective responses.

Front

Levels of Integration

Back

Information processing occurs at cortical, subcortical, and spinal levels. The cortical level handles conscious perception and complex processing, subcortical structures manage automatic functions, and the spinal level mediates reflexes and simple integration.

Front

Grey vs White Matter

Back

Grey matter contains neuronal cell bodies and synapses and is abundant in cortical regions and ganglia. White matter consists mainly of myelinated axons and forms the major communication tracts within the CNS.

Front

Telencephalon Role

Back

The telencephalon includes the cerebral cortex and basal ganglia and is central to voluntary movement, cognition, sensory perception, and memory. The cortical lobes (frontal, parietal, temporal, occipital) specialize in different modalities and higher functions.

Front

Basal Ganglia Function

Back

Basal ganglia are subcortical nuclei that regulate initiation and control of voluntary movements and motor learning. They integrate cortical signals and modulate motor output via thalamic and brainstem circuits.

Front

Diencephalon Components

Back

The diencephalon contains the thalamus and hypothalamus; the thalamus relays and processes most sensory input to the cortex, while the hypothalamus controls autonomic, endocrine, and visceral functions. Together they coordinate sensory integration with homeostatic regulation.

Front

Brainstem Functions

Back

The brainstem controls essential life-support functions such as respiration, cardiovascular regulation, and arousal. It also contains nuclei for many cranial nerves and pathways connecting the forebrain and spinal cord.

Front

Spinal Cord Roles

Back

The spinal cord transmits ascending sensory and descending motor pathways and mediates spinal reflexes. Its segmental organization gives rise to spinal nerves that innervate body regions and effectors.

Front

Cranial and Spinal Nerves

Back

Cranial nerves emerge from the brain and serve head and neck structures, while spinal nerves arise from the spinal cord and innervate the body. Nerve plexuses in cervical, lumbar, and sacral regions reorganize ventral rami to supply limbs.

Front

Dermatomes

Back

Dermatomes are skin areas innervated by sensory fibers from a single spinal nerve root. Mapping dermatomes helps localize spinal lesions or nerve root injuries clinically.

Front

Meninges

Back

Meninges are the protective membranes surrounding the CNS and comprise the dura mater, arachnoid, and pia mater. They cushion the brain and spinal cord and contain the subarachnoid space where cerebrospinal fluid circulates.

Front

Cerebrospinal Fluid

Back

Cerebrospinal fluid (CSF) cushions the CNS, removes metabolites, and transports nutrients; it is produced mainly by the choroid plexuses. CSF circulates through ventricles and the subarachnoid space and is absorbed into venous sinuses.

Front

Hydrocephalus

Back

Hydrocephalus is an abnormal accumulation of CSF leading to increased intracranial pressure and ventricular enlargement. It can result from impaired CSF circulation, absorption, or overproduction and may cause neurological deficits if untreated.

Front

Receptor Classification

Back

Sensory receptors are classified as exteroceptors, telereceptors, proprioceptors, and interoceptors based on stimulus origin. They transduce physical or chemical stimuli into electrical signals for the nervous system to interpret.

Front

Receptor Types

Back

Receptors include mechanoreceptors for pressure and deformation, photoreceptors for light, thermoreceptors for temperature, chemoreceptors for chemical stimuli, and nociceptors for noxious/painful stimuli. Each receptor type has specialized transduction mechanisms and receptive structures.

Front

Receptor Adaptation

Back

Receptors show slow or rapid adaptation: slow-adapting receptors maintain firing during a sustained stimulus, while fast-adapting receptors respond transiently at stimulus onset or offset. Adaptation patterns affect perception of stimulus duration and change.

Front

Nociceptors and Pain

Back

Nociceptors respond to mechanical, thermal, and chemical stimuli that can damage tissue and initiate pain signaling. Pain can be nociceptive (physiological) or neuropathic (due to nervous system injury), and may present as fast sharp pain or slow diffuse pain.

Front

Pain Pathways

Back

Ascending pain information travels via pathways such as the anterolateral system and trigeminothalamic tracts to reach thalamus and cortex. These pathways convey localization, intensity, and affective aspects of pain for cortical processing.

Front

Pain Modulation

Back

Endogenous pain modulation involves descending pathways from brainstem and cortical centers that inhibit or facilitate spinal nociceptive transmission. Neurotransmitters like endogenous opioids, serotonin, and noradrenaline play roles in this modulation.

Front

Referred Pain

Back

Referred pain occurs when visceral and somatic afferents converge onto the same spinal neurons, causing visceral pain to be perceived in a somatic region. The convergence-projection theory explains why visceral pathology can present with somatic pain patterns.

Front

Headache Types

Back

Tension-type headache is characterized by bilateral, pressing pain often related to muscle tension, while migraine is a recurrent unilateral throbbing headache often accompanied by nausea and photophobia. Migraine involves cortical excitability, neurogenic inflammation, and distinct clinical phases.

Front

Somatosensory Homunculus

Back

The somatosensory homunculus is a cortical map in the postcentral gyrus showing disproportionate representation of body regions according to sensory innervation density. It explains why hands and face occupy large cortical areas relative to their size.