BIO 120 UNIT 4

sensory input

the information gathered by the body's sensory receptors about the internal and external environment

integration of information

the process where sensory information is processed and interpreted to generate appropriate responses

somatic nervous system

governs voluntary muscle movements

automatic nervous system

regulates involuntary functions like gland secretion and smooth muscle activity

maintenance of homeostasis

the body's ability to maintain a stable internal environment, by rapidly sensing and responding to changes in both the internal and external environment

central nervous system (CNS)

brain and spinal cord ■ The control center of the body ■ Receives, processes and integrates information from the body and the external environment and generates responses

peripheral nervous system (PNS)

somatic and autonomic nervous systems that connect the CNS to the limbs and organs.

somatic nervous system

controls voluntary movements and sensory input from the body to the central nervous system

autonomic nervous system

Regulates involuntary physiologic processes including heart rate, blood pressure, respiration, digestion, and sexual arousal

• sympathetic and parasympathetic nervous system

sympathetic nervous system

triggers fight or flight by increasing heart rate, blood pressure and respiration

parasympathetic nervous system

conserve energy and promote a rest and digest state

enteric nervous system

determines the movements of the GI tract

sensory neurons

afferent, convert stimuli from the environment (like light, sound, or touch) into electrical signals that the nervous system can interpret

motor neurons

efferent, transmit signals from the brain and spinal cord to muscles and glands, enabling movement and other bodily functions

interneurons

within CNS for integration, a type of neuron located in the central nervous system (brain and spinal cord) that act as intermediaries between sensory neurons and motor neurons

anaxonic neurons

lack axons, a type of neuron characterized by the absence or indistinguishability of an axon from their dendrites

axon hillock

site of action potential initiation, a specialized region of a neuron's cell body (soma) where the axon originates

astrocytes

regulate neurotransmitters, clearing excess neurotransmitters, stabilizing and regulating the blood-brain barrier, and promoting synapse formation

microglia

immune defense, a class of brain cells that act as immune effector cells in the central nervous system, displaying functions such as phagocytosis, antigen presentation, and production of various immune-related molecules

ependymal cells

produce/move CSF (ciliated) - They line the spaces (called ventricles and the central canal) where cerebrospinal fluid (CSF) flows. ■ They help produce and circulate this fluid, which cushions your brain and spinal cord and helps remove waste. ■ These cells have tiny hair-like structures called cilia that help move the fluid around.

oligodendrocytes

myelinate axons, responsible for creating and maintaining the myelin sheath around axons

schwann cells

myelinate axons, they form the myelin sheath around axons in the PNS, which speeds up nerve impulse transmission ■ play a role in nerve regeneration after injury

membrane potentials

the electrical potential difference across a cell's membrane, resulting from the uneven distribution of ions ● Resting: ~ -70 mV ● Threshold: ~ -55 mV

ligand gated

triggered by neurotransmitters ○ a type of membrane receptor that open or close in response to the binding of a specific molecule, known as a ligand, like a neurotransmitter

voltage gated Na+

opens at threshold → depolarization ○ transmembrane proteins that open in response to a change in the membrane potential, allowing sodium ions to flow across the cell membrane

voltage gated K+

opens later → repolarization ○ transmembrane proteins that allow potassium ions to pass through the cell membrane in response to changes in membrane potential

action potential

1. At -55mV (threshold), voltage-gated Na+ channels open (activation gate) 2. after which, voltage-gated Na+ channel inactivation gate closes 3. Next, voltage-gated K+ channels open 4. Then, Ca²⁺ channels open at axon terminals 5. Finally, synaptic vesicles fuse with the plasma membrane to release neurotransmitter

absolute

no new AP possible

relative

new AP possible with strong stimulus

Electrical synapses

gap junctions (connexons): Faster than chemical synapses ○ a protein structure composed of six connexin proteins that forms a half-channel in the cell membrane ○ a specialized structure that allows for the direct transfer of electrical signals between neurons, or between neurons and other cells, through specialized channels

chemical synapses

Neurotransmitter diffuses across synapse to bind receptor, a specialized junction between two nerve cells (neurons) or between a neuron and a muscle or gland cell, where a chemical signal (neurotransmitter) is released from one cell to transmit information to the other

glutamate

a crucial amino acid and a primary excitatory neurotransmitter in the central nervous system

GABA

Inhibitory, causes IPSPs via Cl⁻ channels ○ a naturally occurring amino acid in the brain and a key inhibitory neurotransmitter

serotonin

playing a key role in mood regulation, sleep, digestion, and other bodily processes

spatial summation

Multiple inputs from different synapses ○ a process where multiple weak signals, each individually insufficient to trigger a response, combine to produce a stronger signal that can reach a neuron's threshold and cause it to fire

temporal summation

Repeated inputs from the same synapse ○ the process where repeated, rapid stimuli are combined to produce a stronger effect or response than a single stimulus

filum terminale

Extension of the inferior spinal cord pia mater ■ the process where repeated, rapid stimuli are combined to produce a stronger effect or response than a single stimulu

cauda equina

Nerves extending from the inferior spinal cord ■ a bundle of spinal nerves located at the lower end of the spinal cord, resembling a horse's tail

cervical enlargement

C3–T1 ■ a thickening or widening of the spinal cord in the neck region (cervical area) that houses the nerves supplying the upper limbs

dura mater

Superficial meninge superficial to epidural space ■ the outermost, toughest layer of the three meninges that protect the brain and spinal cord

spinal nerves

31 pairs total ○ 8 pairs cervical, 12 pairs thoracic, 5 pairs lumbar, 5 pairs sacral, 1 pair coccygeal

pia

the innermost layer of the three meninges, which are the protective membranes surrounding the brain and spinal cord

arachnoid

the middle layer of the three meninges, which are the protective membranes surrounding the brain and spinal cord

epineurium

the outermost layer of connective tissue that surrounds a peripheral nerve. It's composed of dense irregular connective tissue and acts as a protective sheath, containing blood vessels and lymphatics that supply the nerve

perineurium

It wraps around small bundles of nerve fibers (called fascicles), kind of like how a plastic wrapper holds together a bunch of wires in a cable. It helps protect the nerves from damage and keeps the nerve signals inside safe and organized. It also helps control what gets in and out of the nerve bundle, acting like a filter or barrier.

endoneurium

a delicate layer of connective tissue that surrounds individual nerve fibers in a peripheral nerve. It's the innermost layer, enclosing the myelin sheath of each axon and separating it from neighboring nerve fibers. This layer plays a crucial role in nerve function, including nerve signal isolation and maintaining endoneurial fluid pressure.

ipsilateral

belonging to or occurring on the same side of the body

contralateral

Having to do with the opposite side of the body

monosynaptic

Stretch reflex primary arc (muscle to spinal cord to same muscle of a reflex pathway) involving a single synapse.

polysynaptic

a neural pathway or reflex involving multiple synapses (more than one) between neurons

muscle spindle

sensory receptors located within muscles that detect changes in muscle length and the speed of those changes

golgi tendon organ

Sensory receptor that initiates Golgi tendon reflex

• specialized sensory receptors located at the junction of muscles and tendons

excitatory interneurons

activate the antagonist muscle

inhibitory interneurons

inhibit the antagonist muscle

cerebrum

organized as lobes; conscious thought ○ responsible for higher-level functions like conscious thought, voluntary movement, and sensory perception

cerebellum

includes arbor vitae; motor coordination ○ a crucial part of the central nervous system located at the back of the head, below the cerebrum and above the brainstem. It plays a vital role in coordinating movement, maintaining balance, and regulating muscle tone

pons

involved in various functions, including sleep, respiration, and facial expressions, and also serves as a connection point between the forebrain and the cerebellum

medulla oblongata

includes pyramids and olives ■ regulating essential autonomic functions and relaying signals between the brain and spinal cord

superior colliculi

vision, a structure in the midbrain that plays a crucial role in orienting behavior and visual attention

inferior colliculi

auditory,primarily responsible for processing auditory information and coordinating acoustic-motor functions

substantia nigra

dopamine, damage causes Parkinson’s Disease ● a brain structure located in the midbrain, part of the basal ganglia, and plays a crucial role in movement, reward, and learning

thalamus

Largest structure of the diencephalon; relay station for sensations ■ a crucial brain structure that acts as a central relay station for sensory and motor information, as well as playing a role in sleep, alertness, and consciousness

hypothalamus

a structure deep within your brain. It's the main link between your endocrine system and your nervous system. Your hypothalamus keeps your body balanced in a stable state called homeostasis.

pineal gland

help control the circadian cycle of sleep and wakefulness by secreting melatonin

habenula

Addiction

■ a small brain structure located in the epithalamus, divided into medial and

lateral divisions, that plays a crucial role in regulating various behaviors

and is implicated in several neuropsychiatric disorders

subthalamus

Helps coordinate motor functions ■ a crucial component of the basal ganglia circuit, playing a significant role in motor control, specifically in inhibiting unwanted movements

limbic system

Involved in motivation and memory

choroid

a secretory tissue responsible for producing cerebrospinal fluid (CSF) in the vertebrate brain

largest ventricle

: lateral (superior/inferior horns) ○ The ventricles are interconnected and filled with cerebrospinal fluid (CSF), which plays a vital role in protecting the brain and spinal cord, and also facilitates the transport of nutrients and waste

cerebral aqueduct

a narrow channel in the brain that connects the third and fourth ventricles. It is a crucial part of the ventricular system, allowing cerebrospinal fluid (CSF) to flow between these two ventricles. This flow is essential for maintaining proper brain function and cushioning the brain

association fibers

bundles of nerve fibers (axons) that connect different areas of the cerebral cortex within the same hemisphere

commissural fibers

nerve fibers that connect the two hemispheres of the brain, allowing for communication and coordination between them

projection fibers

nerve fibers that connect the cerebral cortex to other parts of the central nervous system, including the brainstem, spinal cord, and subcortical structures like the thalamus

gyri

bulges ○ the ridges or folds on the surface of the cerebral cortex of the brain

sulci

shallow grooves ○ the grooves or indentations on the surface of the cerebral cortex

fissures

deep grooves or furrows that divide the brain into lobes and hemispheres

frontal lobe

(anterior) manage thinking, emotions, personality, judgment, self-control, muscle control and movements, memory storage and more

parietal

processing sensory information, spatial reasoning, and certain aspects of language and mathematical ability

temporal

(lateral) plays a crucial role in processing auditory information, memory, and language

insula

(deepest/smallest) plays a crucial role in various functions, including processing emotions, self-awareness, and sensory experiences like taste and pain

cranial nerve 1

olfactory - smell

cranial nerve 2

optic - vision

cranial nerve 5

trigeminal - facial sensation

cranial nerve 7

facial - facial expressions

cranial nerve 10

vagus - heart rate, parasympathetic

dermatome

skin area innervated by one pair of spinal nerves

brachial plexus

upper limbs

lumbosacral plexus

lower limbs

cervical plexus

neck

Choroid plexus (ependymal cells line ventricles)

CSF production and flow

occipital

(posterior) the visual processing center of the brain, located at the back of the head