The Brain

Outer Brain

  • The brain sits in Cerebral Spinal Fluid:

    • CSF: Circulating fluid that surrounds the membranes of the brain and spinal cord; provides neural connection to the endocrine system

  • The brain is isolated by the blood stream by membranes called Meninges

    • Meninges: “Three layers of connective tissue that surround and protect the brain and spinal cord”

  • This area is the Blood-Brain barrier

Spinal Cord

The Spinal Cord can be separated into its core and its outer layer

Grey Matter: The tissue of the brain and spinal cord where the cell bodies and dendrites of neurons are located

White Matter: The tissue of the brain and spinal cord, composed primarily of axons of neurons; in the spinal cord, it surrounds the grey matter.

How do signals travel in the spinal cord?

Afferent axons (incoming) enter the dorsal root of the spinal cord and make synapses w

ith interneurons in the grey mater.

The interneurons send axons upward through the white matter of the spinal cord to the brain.

Efferent axons (outgoing) from the interneurons of the brain pass downward through the white matter of the spinal cord and make synapses with the dendrites and cell bodies of efferent neurons in the grey matter of the cord.

Brain

Hindbrain

Medulla Oblongata: The hindbrain region that connects the spinal cord to the cerebellum; important in autonomic nerve control.

Cerebellum: The region that is involved in muscle movement and balance.

  • Connected to Pons

  • receives sensory input from receptors in the muslces and joints

Pons: The brain region that transfers nerve signals between the cerebellum and the medulla

The Medulla and the pons, along with the midbrain, create the brain stem

Forebrain

The forebrain makes up most of the brain mass in humans

Cerebrum: the brain region that is involved in motor activities and sensory information; the largest and most developed region of the brain

Thalamus

“The brain region that interprets sensory input and signals the cerebrum”

Like a switchboard…

Hypothalamus: Contains centres that regulate basic homeostatic functions

Basal Nuclei: Grey-matter centres that surround the thalamus on both sides of the brain.

  • Moderate the voluntary movements that are directed by motor centres of the cerebrum.

Cerebrum (part of forebrain)

Cerebral cortex: The outermost layer of the cerebral hemispheres

  • It is a thin layer of grey matter. It carries out brain functions and is divided into a right and left hemisphere.

  • Split into the frontal, parietal, temporal, and occipital lobes.

The two halves can function separately.

Corpus callosum: thick axon bundles that connect the two cerebral hemispheres.

Midbrain