Nervous System Organization

Describe the two divisions of the autonomic nervous system

Sympathetic: ”Fight or Flight”

• Prepares the body for stressful situations by using norepinephrine at target organs

• Heart rate increases, adrenaline, shallow/quick breaths, pupils feel wider or more alert, cool hands, slight sweat, tense shoulders/jaw, thinking feels very sharp but also rushed. boosts energy release, decreases digestion, and increases blood flow to muscles.

Parasympathetic: ”Rest and Digest”

• Promotes relaxation, energy conservation, and routine bodily maintenance by using acetylcholine at target organs

• Heart rate is calm and reduces blood pressure, slower/deeper breaths, warm hands, relaxed face/shoulder muscles, constricted/normal pupils, stimulates digestive and urinary functions, a little sleepy, thinking is not rushed and expansive.

Explain how sensory and motor functions are mapped in the brain

Motor homunculus (Motor Cortex)

• Precentral gyrus in the frontal lobe sends signals from the brain to muscles for voluntary movement, areas for fine motor control (fingers, face) get more cortical space

• Signals originate in the primary motor cortex, influenced by secondary motor areas, and travel down the corticospinal tract to the spinal cord, then out to muscles. 

• The left motor cortex controls the right side of the body, and vice-versa.

Sensory homunculus (Somatosensory Cortex)

• Postcentral gyrus in the parietal lobe receives and processes sensory input (touch, pain, temperature, pressure) from the body

• Larger cortical areas are dedicated to sensitive body parts (lips, hands, genitals) than less sensitive ones (back, legs)

• Sensory info travels from the body to the spinal cord, up to the thalamus (the brain's relay station), and then to the primary sensory cortex. 

What is fMRi imaging and how is it used to explore organizations in the brain?

It detects minor changes in blood flow and oxygenation levels by measuring the resonance of a magnetic field, showing which brain areas are active during certain tasks.

Areas with more BOLD (blood-oxygen-level-dependent) signal indicate higher neural activity, which is then color-coded onto brain images, creating a "movie" of the brain working

MRI

• Generates a strong magnetic field that aligns the protons (hydrogen nuclei) in the body.

• A radiofrequency (RF) pulse is emitted, which disrupts the alignment of the protons.

• As the protons return to their original alignment, they release RF signals that are detected by the machine

• The detected signals are processed by a computer to create detailed images of the body's tissues and organs

Cortical magnification

The principle that certain sensory areas are disproportionately represented in the brain's cortex. This means that a small area of the sensory surface takes up a much larger area of the brain's primary space for that sense than a peripheral area of the same size. This unequal representation allows for highly detailed processing.

Example: Star nosed moles

• Anatomically their nose and hands are proportional to their bodies, however, they are virtually blind, so to help them navigate, their nose and hand senses are magnified to compensate for the loss of sight. Their cortical magnification shows their nose and hands disproportionately larger than everything else.

Pre and Postganglionic Neurons

Pre: Originate in the CNS (brainstem or spinal cord) and travel to an autonomic ganglion, releasing acetylcholine

Post: Cell bodies are in the ganglion, and their axons extend to the target organs (heart, glands, smooth muscles).

• Sympathetic: release norepinephrine/noradrenaline

• Parasympathetic: Release acetylcholine