brain structure and function

Question 1

What is gray matter and white matter?

Answer 1

GM: Inside, H-shaped structure containing cell bodies and unmyelinated interneurons.

WM: Outside layer of the spinal cord composed of myelinated axons.

Grey = “processing centers” (thinking, decision-making).
White = “highways” (fast communication links).

Question 2

What are dorsal horns and ventral horns?

Answer 2

Dorsal horns are the back parts of the spinal cord gray matter that carry sensory input into the cord.

Ventral horns are the front parts that carry motor output from the cord to the muscles.

Question 3

What are spinal nerves?

Answer 3

31 pairs of nerves that split into two roots before joining the spinal cord.

Question 4

What is the dorsal root and ventral roots?

Answer 4

Each of the 62 spinal nerves divides as it
nears the cord , and its axons are joined
to the cord via one of two roots: the dorsal root or the
ventral root.

Question 5

What is the somatic nervous system?

Answer 5

Part of the nervous system that controls skeletal muscles.

Question 6

What is the autonomic nervous system?

Answer 6

Part of the nervous system that controls internal organs through ganglia.

Question 7

What is the neural tube?

Answer 7

Structure that develops into the central nervous system, initially forming three swellings.

Question 8

What is the hippocampus and why is she special?

Answer 8

The hippocampus is a cortical structure that is not neocortex, since it has only 3 layers (rather than 6).

It lies on the medial edge of the cerebral cortex in the medial temporal lobe, where the cortex folds back on itself.

Its name (hippocampus = “sea horse”) comes from its seahorse-like shape in cross section.

The hippocampus plays a major role in certain kinds of memory.

Question 9

The first indications of the developing brain are three swellings that occur at the anterior end of this tube. These three swellings develop into the ____________.

Answer 9

Forebrain, Midbrain, and hindbrain.

Question 10

The five swellings that compose the developing brain at birth are _____________________.

Answer 10

The telencephalon
The diencephalon
The mesencephalon (or midbrain)
The metencephalon
The myelencephalon (encephalon means “within the head”).

(Te D messed up meeting my mom)

Question 11

Which of the 5 swellings undergo the most growth and what are the other four referred to as?

Answer 11

The telencephalon (the left and right cerebral hemispheres) undergoes the greatest growth during development.

The other four divisions of the brain are often referred to collectively as the brain stem—the stem on which the cerebral hemispheres sit.

Question 12

What is the myelencephalon referred to as?

Answer 12

The myelencephalon is often referred to as
the medulla.

Question 13

What is the myelencephalon (medulla) and the role of the reticular formation?

Answer 13

What is the myelencephalon (medulla) and the role of the reticular formation?

A: The myelencephalon (medulla) carries signals between the brain and body.

It contains the reticular formation, a network of nuclei involved in arousal, sleep, attention, movement, muscle tone, and vital reflexes (cardiac, circulatory, respiratory).

R = Reflexes (heart, breathing, circulation)
A = Arousal/attention
M = Movement & muscle tone
3 = Sleep (zzz)

Question 14

What is the reticular formation also referred to as and why?

Answer 14

Sometimes, the reticular formation is referred to
as the reticular activating system because parts of it seem
to play a role in arousal.

Question 15

What structures make up the metencephalon, and what are their functions?

Answer 15

The metencephalon has two main parts: the pons (ventral bulge with tracts and reticular formation) and the cerebellum (“little brain”).

The cerebellum is vital for sensorimotor control—damage causes loss of precise movement and adaptation. It also affects cognition (decision-making, language), so its role is broader than just movement.

👉 Easy way to remember: “Pons = Pathway, Cerebellum = Coordination + Cognition.”

Question 16

What are the two divisions of the mesencephalon?

Answer 16

A: The mesencephalon has two divisions:

Tectum (roof): dorsal surface of the midbrain.

Tegmentum: ventral to the tectum.

Question 17

What is the tectum, and what structures does it contain?

Answer 17

A: The tectum is the dorsal surface of the midbrain. It contains two pairs of colliculi (“little hills”):

Inferior colliculi (posterior pair): auditory function.

Superior colliculi (anterior pair): visual-motor function, directing orientation toward or away from visual stimuli.
(In lower vertebrates, tectum = entirely visual-motor, called optic tectum.)

Question 18

What is the tegmentum, and what structures does it contain?

Answer 18

A: The tegmentum lies ventral to the tectum. It contains:

Reticular formation and tracts of passage.

Periaqueductal gray: around the cerebral aqueduct; role in analgesic (pain-reducing) effects of opioids.

Substantia nigra (black substance): part of sensorimotor system.

Red nucleus: also part of sensorimotor system.

(Really Tiny Penguins Swim Rapidly”)

Question 19

What two main structures make up the diencephalon?

Answer 19

A: The thalamus and the hypothalamus.

Question 20

Describe the structure of the thalamus.

Answer 20

A: The thalamus is a large, two-lobed structure at the top of the brain stem. Each lobe sits on one side of the third ventricle, joined by the massa intermedia. It has visible white lamina (layers of myelinated axons) and contains many pairs of nuclei that mostly project to the cortex.

Question 21

What is the function of the sensory relay nuclei in the thalamus?

Answer 21

A: They receive signals from sensory receptors, process them, and transmit them to the correct areas of sensory cortex. Examples:

Lateral geniculate nuclei → vision

Medial geniculate nuclei → hearing

Ventral posterior nuclei → touch/somatosensory
They also receive feedback from the cortical areas they project to.

Question 22

Where is the hypothalamus located, and what are its main functions?

Answer 22

A: The hypothalamus lies just below the anterior thalamus. It regulates motivated behaviors like eating, sleep, and sex. It also controls the pituitary gland, which releases hormones.

Question 23

What other structures are found on the inferior surface of the hypothalamus?

Answer 23

Pituitary gland: hangs from the hypothalamus; controls hormone release.

Optic chiasm: where optic nerves meet and partially cross (contralateral = crossing, ipsilateral = same side).

Mammillary bodies: two spherical nuclei, part of the hypothalamus, located behind the pituitary.

Question 24

What is the cerebral cortex made of, and why is it called gray matter?

Answer 24

A: The cerebral cortex is a layer covering the hemispheres, mainly made of small, unmyelinated neurons (gray matter). Beneath it are large myelinated axons (white matter).

Question 25

Q: Why is the human cerebral cortex convoluted?

Answer 25

A: Convolutions (folds) increase surface area of the cortex without increasing brain volume. Large furrows are fissures, small ones are sulci, and ridges are gyri.

Question 26

What separates the cerebral hemispheres, and how are they connected?

Answer 26

They are separated by the longitudinal fissure and connected by cerebral commissures. The largest commissure is the corpus callosum.

Question 27

What fissures divide the hemispheres into lobes?

Answer 27

A: The central fissure and the lateral fissure divide the hemispheres into frontal, parietal, temporal, and occipital lobes.

Question 28

What is the main function of the occipital lobes?

Answer 28

A: Processing and analyzing visual input.

Question 29

Q: What are the functions of the parietal lobes?

Answer 29

The postcentral gyrus analyzes body sensations (e.g., touch). Posterior parietal areas help perceive location of objects and body position, and direct attention.

Question 30

What are the three main functions of the temporal lobe?

Answer 30

Superior temporal gyrus: hearing and language Inferior temporal cortex: identifies complex visual patterns Medial temporal cortex: certain kinds of memory

Question 31

Q: What are the main functions of the frontal lobe?

Answer 31

Precentral gyrus & adjacent cortex: motor control Anterior frontal cortex: complex cognition (planning, decision making, evaluating behavior, assessing others’ actions)

Question 32

How much of the cortex is neocortex, and how is it organized?

Answer 32

A: About 90% of human cortex is neocortex, divided into six layers (I–VI). It shows columnar organization, where vertical columns form mini-circuits for single functions.

Question 33

What are the 1st 3 layers of the neocortex?

Answer 33

Layer I: Axons and dendrites; few cell bodies. Layer II: Densely packed stellate cells; a few small pyramidal cells. Layer III: Loosely packed stellate cells; intermediate-sized pyramidal cells.

Question 34

What are the last 3 layers of the neocoretx?

Answer 34

Layer IV: Bands of densely packed stellate cells; no pyramidal cells. Layer V: Very large pyramidal cells; a few loosely packed stellate cells. Layer VI: Pyramidal cells of various sizes; loosely packed stellate cells.

Question 35

What are the two main types of neocortical neurons?

Answer 35

Pyramidal cells: large multipolar neurons with pyramid-shaped bodies, an apical dendrite, and long axon. Stellate cells: small star-shaped interneurons with short or no axon.

Question 36

What are three key features of neocortical anatomy?

Answer 36

- Two cell types: pyramidal and stellate cells. - Layers differ in size, density, and proportions of cell types. - Axons and dendrites run vertically, creating columnar circuits.