PTA2046 Advanced Brain - Neuroanatomy Flashcards

Flashcards for reviewing Neuroanatomy lecture notes.

Functions of the nervous system

Perceive sensory experiences, initiate movement, perform cognitive tasks.

Two parts the nervous system is divided into

The flexible central nervous system (CNS) and the reliable peripheral nervous system (PNS).

CNS (central nervous system)

Site of information integration and is composed of the brain and spinal cord.

Goal of the CNS

Take in and process all information from outside and within the human body, put meaning to that data, and decide how to control the body's response.

PNS (peripheral nervous system)

Provide robust communication between the CNS and body and comprises all of the components outside the cranium and spine.

The PNS consists of…

Consists of the nerves leading to and from the CNS, including the cranial nerves exiting the brainstem and the spinal roots exiting the spinal cord, many of which combine to form peripheral nerves.

The PNS is divided into…

Somatic nervous system and the autonomic nervous system (ANS).

Somatic nervous system

Composed of sensory nerves (Cranial and peripheral nerves carrying information toward the CNS) and motor nerves (Nerves carrying information from the CNS to the peripheral systems ).

ANS (autonomic nervous system)

Further subdivided into sympathetic and parasympathetic components.

sensory nerves

nerves carrying information toward the CNS.

motor nerves

nerves carrying information from the CNS to the peripheral systems

Types of nerve cells in the nervous system

Neurons and neuroglia.

Neurons

Specialized for communication through their ability to generate rapid electrochemical signals.

Three categories neurons are divided into

Afferent neurons, interneurons, and efferent neurons.

Interneurons

Relay signals between two neurons.

motor neurons (efferent)

Conveys output from the CNS to the muscles motor neurons

sensory neurons (affferent)

Detect environmental or bodily stimuli and relay it to the CNS sensory neurons

Dendrites

Receive signals from other cells.

Cell body

Organizes and keeps the cell functional.

Cell membrane

Protects the cell.

Axon hillock

Generates impulse in the neuron.

Nucleus

Controls the entire neuron.

Node of Ranvier

Allow diffusion of ions.

Schwann cell

Produces the myelin sheath.

Axon

Transfers signals to other cells and organs.

Myelin sheath

Increases the speed of the signal.

Axon terminal

Forms junctions with other cells.

Neuroglia (CNS)

Diverse support cells that facilitate neuron function and survival.

Types of neuroglia

Astrocytes, oligodendrocytes, microglia, and ependymal cells.

Oligodendrocytes

Wrap myelin sheaths around axons, forming the white matter of the CNS.

Microglia

The phagocytes of the CNS; engulf and digest pathogens and assist with nervous system repair after injury.

Ependymal cells

Line the ventricular system, produce and circulate cerebrospinal fluid.

Satellite cells

Buffer extracellular ion concentrations around neuronal cell bodies.

Myelinating Schwann cells

Ensheath axons in myelin, similar to oligodendrocytes.

Neuron structures

consists of dendrites, a cell body, and an axon

Dendrites

responsible for transducing extracellular physical or chemical input into an intracellular signal produces electrical currents, which are transferred to the cell body for processing

Cell body or soma

composed of a nucleus and a number of different cellular organelles; responsible for synthesizing proteins and supporting functional activities of the neuron, such as transmitting electrochemical impulses and repairing cells

Axon

message-sending component of neurons; extend from the cell body and contact target cells that can include muscle cells, glands, or other neurons; communicate through called action potentials down their axon (electrical signals down their axon)

Myelin

increases the efficiency of action potential conduction through: (1) increased conduction velocity, and (2) decreased metabolic expenditure

Multiple sclerosis

neurodegenerative disorder caused by the autoimmune destruction of oligodendrocytes; loss of myelin impairs action potential conduction odemyelinated neurons must continue to spend higher amounts of ATP for each action potential

Myelin insulates the axon because…

myelinated regions of the axon prevents electrical charge from leaking out of the axon

Synapses

site of contact between the axon and its target cell; site at which electrical signals within the axon (i.e., action potentials) are translated into a chemical signal that creates some effect on the target cell; chemical messages are called neurotransmitters

Neurotransmitters

chemicals that are released from neurons to communicate with target cells

common neurotransmitters

acetylcholine, glutamate, γ-aminobutyric acid, dopamine, serotonin, and norepinephrine

Acetylcholine

conveys information in the PNS; neurotransmitter used by lower motor neurons that synapse onto skeletal muscle fiber; also plays a role in regulating heart rate and other autonomic functions

Glutamate

excitatory neurotransmitter used widely throughout the CNS; Excessive glutamate release is thought to contribute to neuron destruction after an injury to the CNS

γ-Aminobutyric acid (GABA)

major inhibitory neurotransmitter of the brain; glycine is the major inhibitory neurotransmitter of the spinal cord

Dopamine

influences motor activity, motivation, general arousal, and cognition

Serotonin

plays a role in mood, behavior, and inhibits pain

Norepinephrine

used by the sympathetic nervous systems; produces the “fight-or-flight response” to stress

CNS components

brain and spinal cord Protective structures include the Bony skull and vertebral column and the meninges

Dura mater

outermost layer; thick, fibrous connective tissue membrane that adheres to the skull; two distinct projections of dura: the falx cerebri, which separates the cerebral hemispheres; tentorium cerebelli, which provides a separation between the posterior cerebral hemispheres and the cerebellum

epidural space

area between the dura mater and the skull, it is a potential space (only exists in the case of injury, epidural space should not be visible)

Arachnoid mater

middle layer; subdural space is a potential space lies between the dura and the arachnoid, subarachnoid space: Below the arachnoid mater, bona fide space; contains the cerebral arteries; filled with cerebrospinal fluid, which allows it to act as a cushion for the CNS

Pia mater

third layer; innermost layer and adheres to the brain and spinal cord; delicate and fairly permeable compared with the other layers; Mostly, meninges are continuous with the connective tissues found in peripheral nerves

Cerebral cortex

surface of the cerebrum or cerebral cortex is composed of depressions (sulci) and ridges (gyri); outer surface of the cerebrum, approximately 2 to 4 mm thick; inner surface of the cerebrum

Lobes of the cerebrum

frontal, parietal, temporal, and occipital

Frontal lobe

contains the primary motor cortex (PMC); responsible for voluntary control of complex motor activities; exhibits a strong influence over cognitive functions, including judgment, attention, awareness, abstract thinking, mood, and aggression; Broca area (principal motor region responsible for speech) is located within the frontal lobe, near the primary motor regions that control the lips, tongue, and larynx

Parietal lobe

contains the primary somatosensory cortex; Incoming sensory information is processed within this lobe, meaning is provided to the stimuli; Perceptual learning requires a functioning parietal lobe (Perception: process of attaching meaning to sensory information and requires interaction between the brain, body, and the individual’s environment)

Temporal lobe

contains the primary auditory cortex (decodes pitch and volume of sounds; meaning of sounds is distinguished in other cortical regions); Wernicke area: ascribes meaning to particular sounds (i.e., words); involved in declarative memory function (i.e., factual memories); important memory-relevant structures like the amygdala and hippocampus are located in temporal lobe

Occipital lobe

contains the primary visual cortex (distinguishes fine details of an image (e.g., line angles); meaning of these fine details are determined in association regions)

Primary cortices

deal with granular details

Association cortices

create meaning from these details Example: neurons in the primary visual cortex are responsive to very specific visual stimuli, such as the angle of a line, whereas visual association cortices will construct objects (e.g., an octagon) and ascribe meaning to these objects (e.g., a stop sign); responsible for all higher-order functions of the CNS, including personality, intelligence, memory, and consciousness

PMC (primary motor cortex)

located in the frontal lobe, primarily responsible for contralateral voluntary control of the upper and lower extremity and facial movements;neurons are organized around movements, lower motor neurons in the spinal cord are organized around muscles

premotor area

well-patterned, bilateral movements and directs our movements based more on external cues (i.e., sensory information)

supplementary motor area (SMA)

eye control and appears to create sequences of movements based more on internal cues (i.e., learned information)

Dominant hemisphere functions

processes information in a sequential, organized, logical, and linear manner; Language is produced and processed in the frontal, temporal, and parietal lobes of the dominant hemisphere; Broca area - plans movements of the mouth to produce speech; Wernicke area - attributes meaning to word

Nondominant cerebral hemisphere

nonverbal and artistic abilities; processes information in a complete or holistic fashion without specifically reviewing all the details, able to grasp or comprehend general concepts responsible for determining spatial relationships

Corpus callosum

large group of axons that connect the right and left cerebral hemispheres and allow communication between the two cortices

Subcortical structures

deep within the brain, include the internal capsule, the basal ganglia, and the limbic system

Internal capsule

contains the major projection fibers that run to and from the cerebral cortex ; lesion within the internal capsule typically causes contralateral loss of voluntary movement and conscious somatosensation, visual and auditory deficits occur rarely

Basal ganglia

group of nuclei located at the base of the cerebrum forms a subcortical structure made up of the caudate nucleus, putamen, globus pallidus, substantia nigra, and subthalamic nuclei; project to motor regions of the thalamus to regulate posture and muscle tone, as well as volitional and automatic movements

bradykinesia

slowed movement

hypokinesia

reduced movement amplitude

akinesia

a lack of movement

Limbic system

group of deep brain structures that are involved in memory and emotion controls memory, pain, pleasure, rage, affection, sexual interest, fear, and sorrow plays a critical role in retention of new memory, retrieval of past memory, and communication with higher brain structures

Thalamus

area where the major sensory tracts (dorsal columns and lateral spinothalamic) and the visual and auditory pathways synapse; serves as a central relay station for sensory impulses, channels them to appropriate primary and association areas of the cortex for interpretation

Hypothalamus

regulates homeostasis, which is the maintenance of a balanced internal environment; involved in automatic functions, including the regulation of hunger, thirst, digestion, body temperature, blood pressure, sexual activity, and sleep-wake cycles; responsible for integrating the functions of both the endocrine system and the ANS through its regulation of the pituitary gland and its release of hormones

Brainstem

located between the thalamus and the spinal cord and is divided into three sections (midbrain, pons, and medulla)

Midbrain

connects the diencephalon to the pons, acts as a relay station for tracts passing between the cerebrum and the spinal cord or cerebellum, houses reflex centers for visual, auditory, and tactile responses

Pons

contains bundles of axons that travel between the cerebellum and the rest of the CNS, functions with the medulla to regulate breathing rate, chewing, and swallowing; contains reflex centers that assist with orientation of the head in response to visual and auditory stimulation

Medulla

extension of the spinal cord and contains the fiber tracts that run through the spinal cord Motor and sensory nuclei for the neck and mouth region are located within the medulla, as well as the control centers for heart rate and respiration

Reticular formation

collection of relay nuclei within the brainstem that extends vertically throughout its length; adjust an individual’s level of arousal, including sleep-wake cycles; facilitates the voluntary and autonomic motor responses necessary for certain self-regulating, homeostatic functions, involved in the modulation of muscle tone throughout the body

Cerebellum

controls balance and complex muscular movements uses primarily proprioceptive information from the head and body and sends that information back to modify muscle and joint activity structure compares the blueprint for a movement to the final product and makes the necessary adjustments

Vermis

controls the trunk and central regions of the body and assists in balance and posture

Hemispheres

control the limbs and allows us to smoothly execute complex, multijoint movements

Spinal cord

direct continuation of the brainstem, specifically the medulla; two primary functions: coordination of movement patterns and communication of sensory information; extends approximately to the level of the intervertebral disc between the first two lumbar vertebrae

Gray matter

areas that contain large numbers of nerve cell bodies and dendrites cell bodies give the region its grayish coloration covers the entire surface of the cerebrum and is called the cerebral cortex

White matter

composed of axons and associated glia high concentration of myelin appear white because of the fat content within the myelin

Gray matter Inside the spinal cord

H-shaped or butterfly-shaped pattern, contains cell bodies of motor and sensory neurons, as well as interneurons that link motor and sensory neurons to create spinal circuits; ventral or anterior horns house the lower motor neurons, dorsal or posterior horns house sensory neurons

white matter Inside the spinal cord

composed of sensory (ascending) and motor (descending) fiber tracts carry impulses between the spinal cord and brain fiber tracts cross over from one side of the body to the other at various points within the spinal cord and brain

Dorsal or posterior columns

carry information about position sense (proprioception), vibration, two-point discrimination, and deep touch

Spinothalamic tract

transmits pain and temperature sensations part of a larger collection of fibers called the anterolateral tract; conveys crude touch and nociceptive input to brainstem nuclei to carry out reflexive responses to painful stimuli

Corticospinal tract

Primary motor pathway; controls skilled movements of the extremities; originates from upper motor neurons in the frontal lobes to stimulate individual muscles to cause contraction and carry out movements

Vagus nerve

major component of the parasympathetic ANS, innervating the myocardium and the smooth muscles of the lungs and digestive tract

Cerebral circulation supply

Anterior cerebral circulation is supplied by the internal carotid arteries. Posterior cerebral circulation is supplied by the vertebral arteries.

Which artery gets blocked the most?

The middle cerebral artery (MCA) is the most frequently blocked artery in stroke patients

Which myelin producing cell allows for axon regrowth?

Oligodendrocytes.

Neurapraxia

A transient physiological block of nerve conduction without axonal disruption. Recovery is typically rapid.

Axonotmesis

Involves disruption of the axon and myelin sheath but preservation of the nerve's connective tissue framework. Wallerian degeneration occurs, and recovery requires axonal regeneration.