KN 232 - Week 8 Structure List

Neuron

- The structural unit of the nervous system

- Collectively, neurons receive information, conduct electrical signals, and release neurotransmitters

Cell body (perikaryon or soma)

- The main part of the neuron; its plasma membrane encloses the cytoplasm, and it contains the nucleus

- Receives input from dendrites, initiates some graded potentials, and conducts these potentials toward the axon

Nucleus

- An organelle located inside the cell body

- Contains DNA and controls cell activities

Nucleolus

- A dense region inside the nucleus

- Produces components needed to make ribosomes

Mitochondria

- Organelles found in the cell body

- Produce ATP to supply energy for cellular activities

Chromatophilic substance (Nissl bodies / rough ER)

- Made of free and bound ribosomes in the cell body

- Ribosomes synthesize proteins

Dendrites

- Short, unmyelinated processes that branch off the cell body

- Receive input and transfer it to the cell body

Axon

- A long process extending from the cell body; it attaches at the axon hillock and ends in terminal branches

- Conducts action potentials and releases neurotransmitters at synaptic knobs

Axolemma

- The plasma membrane surrounding the axon

- Conducts action potentials as voltage-gated channels open sequentially along the membrane

Axon hillock

- The triangular region of the cell body where the axon attaches

- Incoming signals are summed; if threshold is reached at the initial segment, an action potential is generated

Myelin

- Several layers of glial-cell membrane wrapped around an axon; its high lipid content gives it a glossy-white appearance

- Insulates the axon and allows faster action-potential propagation

Schwann cells (neurolemmocyte)

- Elongated, flat glial cells that wrap around axons in the peripheral nervous system

- Form myelin around PNS axons, allowing faster action-potential propagation

Nodes of Ranvier (neurofibril node)

- Gaps between adjacent myelin-wrapped segments of an axon

- Allow action potentials to be regenerated along the axon, supporting faster conduction

Oligodendrocytes

- Glial cells in the central nervous system (CNS) with extensions that wrap around axons

- Form myelin around portions of multiple axons

Terminal branches (telodendria)

- Branches at the end of an axon

- Lead to synaptic knobs that release neurotransmitters to communicate with other cells

Axon terminal (synaptic knob / terminal bouton)

- The enlarged tip at the end of a telodendrion

- Releases neurotransmitters from synaptic vesicles

Vesicle (synaptic vesicle)

- A small sac inside a synaptic knob that contains neurotransmitters

- Releases neurotransmitters when an arriving action potential triggers calcium entry into the synaptic knob

Neurotransmitter

- A chemical messenger synthesized by neurons and stored in vesicles in synaptic knobs

- Is released, binds to receptors on a target cell, and triggers a physiological response

Brain

- An organ of the central nervous system

- Processes information and helps coordinate responses to sensory input

Cerebrum

- A major region of the brain consisting of two cerebral hemispheres

- Involved in conscious sensation, voluntary movement, memory, and other higher functions

Cerebral hemispheres

- The left and right halves of the cerebrum, separated by the longitudinal fissure

- Contain the cerebral lobes and areas involved in processing sensory information and controlling movement

Frontal lobe

- A lobe located toward the front of the cerebrum

- Contains the primary motor cortex, which controls voluntary skeletal muscle movement

Precentral gyrus (Primary motor cortex)

- A ridge of the frontal lobe just anterior to the central sulcus

- Controls voluntary skeletal muscle movement

Parietal lobe

- A cerebral lobe behind the frontal lobe

- Processes somatic sensory information, such as touch and body position

Postcentral gyrus (Primary somatosensory cortex)

- A ridge of the parietal lobe just posterior to the central sulcus

- Receives and processes sensory information from the body, including touch

Occipital lobe

- A lobe at the back of the cerebrum

- Processes visual information

Temporal lobe

- A cerebral lobe on the side of the brain, below the lateral sulcus

- Involved in hearing, memory, and language processing

Brainstem

- A region connecting the brain with the spinal cord; it includes the midbrain, pons, and medulla oblongata

- Relays information and helps regulate essential involuntary functions

Cerebellum

- A brain region behind the brainstem and beneath the posterior cerebrum

- Helps coordinate movement, balance, posture, and motor control

Arbor vitae

- The tree-like branching pattern of white matter inside the cerebellum

- Carries signals within the cerebellum and between it and other nervous system regions

Vermis

- The narrow midline region connecting the two cerebellar hemispheres

- Helps coordinate posture and movements of the trunk

Fissures / sulci

- Grooves on the brain's surface; sulci are generally shallower, while fissures are deeper

- Mark boundaries between brain regions

Central sulcus

- A groove between the frontal and parietal lobes

- Separates the precentral gyrus (primary motor cortex) from the postcentral gyrus (primary somatosensory cortex)

Lateral sulcus

- A prominent groove on the side of the cerebrum

- Separates the temporal lobe from portions of the frontal and parietal lobes

Longitudinal fissure

- The deep groove between the left and right cerebral hemispheres

- Separates the cerebrum into its two hemispheres

Transverse fissure

- A deep groove between the cerebrum and cerebellum

- Marks the boundary between these two brain regions

Parieto-occipital sulcus

- A groove marking the boundary between the parietal and occipital lobes, most clearly seen on the medial brain surface

- Marks the separation between these lobes

Pons (extra)

- A rounded region of the brainstem

- Relays signals and contributes to the regulation of breathing

Medulla oblongata

- The lowest part of the brainstem, continuous with the spinal cord

- Helps regulate vital involuntary functions, including breathing, heart rate, and blood pressure