PNS- automatic and somatic nervous systems

Central Nervous System (CNS)

Consists of the brain and spinal cord; processes and coordinates sensory data and motor commands.

Gray Matter

Unmyelinated cell bodies, dendrites, and axon terminals.

White Matter

Myelinated axons that appear white.

Tracts

Bundles of axons in the CNS (similar to nerves in the PNS).

Cerebrum

Two hemispheres connected by the corpus callosum; each hemisphere has 4 lobes.

Frontal Lobe

Responsible for reasoning, planning, and voluntary movement (motor).

Parietal Lobe

Processes touch, temperature, and pain.

Temporal Lobe

Responsible for hearing and smell.

Occipital Lobe

Responsible for vision.

Gyri

Ridges in the brain that increase surface area for more processing power.

Sulci

Grooves in the brain that increase surface area for more processing power.

Sensory Areas

Receive and process sensory information.

Motor Areas

Control voluntary movement.

Association Areas

Integrate sensory and motor information.

Primary Somatic Sensory Cortex

Located in the parietal lobe; processes touch, temperature, pain, and body position.

Visual Cortex

Located in the occipital lobe; responsible for vision.

Olfactory Cortex

Located in the temporal lobe; responsible for smell.

Auditory Cortex

Located in the temporal lobe; responsible for hearing.

Gustatory Cortex

Located in the frontal lobe; responsible for taste.

Primary Motor Cortex

Located in the frontal lobe; controls voluntary movement.

Wernicke's Area

Located in the temporal lobe; responsible for language comprehension.

Broca's Area

Located in the frontal lobe; responsible for speech production.

Thalamus

Sensory relay station (except smell).

Hypothalamus

Regulates homeostasis and circadian rhythms (via suprachiasmatic nucleus).

Pituitary Gland

Controls hormone secretion.

Pineal Gland

Secretes melatonin.

Medulla Oblongata

Controls involuntary functions such as breathing, vomiting, and blood pressure.

Pons

Connects cerebellum and cerebrum; helps with breathing.

Midbrain

Controls eye movement and visual/auditory reflexes.

Cerebellum

Coordinates movement and balance; contains most brain neurons.

Meninges

Three protective layers around the brain and spinal cord.

Cerebrospinal Fluid (CSF)

Cushions and protects the brain/spinal cord; produced by choroid plexus.

Blood-Brain Barrier (BBB)

Protects the brain by preventing harmful substances from entering.

Reflexes

Spinal-level responses, bypassing the brain for speed.

Pain Types

Two types: fast (sharp, stabbing) and slow (dull, throbbing).

Referred Pain

Occurs when multiple sensory neurons share a single ascending tract.

Chronic Pain

Poorly understood and varies by experience.

Transduction

Converts sensory input into electrical signals once a threshold is reached, changing the membrane potential.

Receptive Field

Area covered by a sensory receptor; neighboring fields can overlap.

Sound Localization

Depends on timing and intensity differences between the ears.

CNS

Central nervous system that integrates sensory information, deciding which inputs require action or can be ignored.

Perceptual Threshold

The level at which a stimulus is perceived, such as adapting to a perfume smell.

Stimulus Properties

Four properties determined by the CNS: Modality, Location, Intensity, Duration.

Tonic Receptors

Adapt slowly; help with fine-tuning (e.g., balance).

Phasic Receptors

Adapt quickly; stop firing after constant exposure (e.g., perfume smell).

Neuron Pathways

Primary neurons detect touch, proprioception, temperature, and pain/itch.

Pacinian Corpuscles

Detect vibration (large receptive fields).

Warm and Cold Receptors

Function within specific temperature ranges; extremes activate nociceptors.

Somatic Motor Neurons

Control skeletal muscles (voluntary).

Autonomic Neurons

Control smooth muscle, cardiac muscle, glands, adipose tissue (involuntary).

Sympathetic Nervous System

Fight or Flight responses, thoracic/lumbar origin, norepinephrine → adrenergic receptors (α, β).

Parasympathetic Nervous System

Rest and Digest functions, brain stem origin, ACh → muscarinic receptors.

Homeostasis

Maintained through a balance between sympathetic and parasympathetic systems.

Preganglionic Neurons

CNS→ganglion.

Postganglionic Neurons

Ganglion→effector.

Vagus Nerve

Cranial Nerve X: 75% of parasympathetic fibers.

Neurotransmitters

Cholinergic (ACh) and Adrenergic (NE/Epi) with specific receptor types.

Somatic Motor Division

1 neuron, always excitatory, uses ACh at neuromuscular junction.

Short Reflex

Bypasses CNS (autonomic).

Proprioception

our sense of body position

Parasympathetic pathway

ACH - nicotinic receptor - Ach - muscarinic receptor

sympathetic pathway

ACh - (nicotinic receptor) -

norepinephrine - adrenergic receptor

preganglionic

referring to neurons in the autonomic nervous system that run from the central nervous system (brain and sc) to the autonomic ganglia

postganglionic

referring to neurons in the autonomic nervous system that run from the autonomic ganglia to various targets in the body (connects to effectors)

Long Reflex

Involves CNS (somatic).

Somatosensory receptors

Specialized receptors for hearing and touch.

Chemoreceptors

Specialized receptors for taste and smell.

Mechanoreceptors

Specialized receptors for touch and pressure.

Osmoreceptors

Specialized receptors for body fluid concentration.

Thermoreceptors

Specialized receptors for temperature changes.

Proprioceptors

Specialized receptors that sense body position in space (joints and muscles).