Lec 35: Nervous System (Part 4)

Central Nervous System consists of what?

The spinal cord and brain

The central nervous system has how many layers of protection?

Three- a hard bony vertebral column and skull, the meninges (dura matter, arachnoid matter, and pia matter), and subarachnoid space

A hard bony vertebral column and skull provide what type of protection?

A protective layer for the CNS

The meninges:

Three connective tissue coverings that encircle the spinal cord and brain

From superficial to deep, what are the meninges?

Dura mater, arachnoid mater, pia mater

Dura mater:

A thick strong layer of dense connective tissue

Arachnoid mater:

Is named for the spider web arrangement of delicate collagen fibers and some elastic fibers

Pia mater:

A thin, transparent layer that adheres to the spinal cord and brain

The pia mater consists of what type of cells and structures?

Thin squamous to cuboidal cells and many blood vessels

Subarachnoid space:

A space between the arachnoid mater and pia mater that contains shock-absorbing cerebrospinal fluid

The spinal cord:

Provides quick reflexive responses to many stimuli

The spinal cord also does what regarding sensory input?

Is the pathway for sensory input to the brain

The spinal cord acts as what for motor output?

The route of motor output from the brain

A transverse section of the spinal cord reveals what?

White matter surrounding an inner core of gray matter

White matter:

Mostly nerve fibers linking different levels of the spinal cord with each other and with the brain

White matter nerve fibers are what type, giving them their color?

Myelinated

The gray horns divide the white matter into what?

Three broad areas called columns

The three white matter columns are what?

Anterior, posterior, and lateral white columns

Each white column contains what?

Distinct bundles of axons having a common origin or destination and carrying similar information

Bundles of axons that extend long distances in the spinal cord are called what?

Tracts

Sensory tracts consist of what?

Axons that carry nerve impulses toward the brain

Motor tracts consist of what?

Axons that carry nerve impulses from the brain

Tracts are bundles of axons in the _____, whereas nerves are bundles of axons in the _____

CNS; PNS

Gray matter:

The cells that lie within the core of the spinal cord

Gray matter is shaped like what?

The letter H or a butterfly

Clusters of neuronal cell bodies form what?

Functional groups called nuclei

Gray matter consists of what?

Dendrites and cell bodies of neurons, unmyelinated axons, and neuroglia

The gray matter is subdivided into what regions?

Horns

Posterior (dorsal) gray horns contain what?

Axons of incoming sensory neurons and interneurons

Anterior (ventral) gray horns contain what?

Somatic motor neuron cell bodies for skeletal muscle contraction

Between posterior and anterior gray horns are what?

Lateral gray horns

Lateral gray horns are found only in what regions?

Thoracic and upper lumbar segments

Lateral gray horns contain what?

Autonomic motor nuclei

On average, each neuron in the brain forms how many synapses?

1000

Blood flows to the brain mainly through what arteries?

Internal carotid and vertebral arteries

The brain represents about what percent of body weight but uses about what percent of oxygen and glucose?

2%; 20%

The blood-brain barrier consists mainly of what?

Tight junctions sealing endothelial cells of brain capillaries

The blood-brain barrier also includes what structure around capillaries?

A thick basement membrane

Astrocytes do what at the blood-brain barrier?

Maintain tight junctions by secreting chemicals

What substances easily cross the blood-brain barrier?

Lipid soluble substances, steroid hormones, and water

How do lipid-soluble substances cross the blood-brain barrier?

Diffusion across lipid bilayer

Glucose crosses the blood-brain barrier by what?

Facilitated transport

Most ions cross the blood-brain barrier how?

Very slowly

Proteins cross the blood-brain barrier how?

They do not pass at all

The four major parts of the brain are what?

Brainstem, cerebellum, diencephalon, cerebrum

Brainstem:

Is continuous with the spinal cord

The brainstem consists of what?

Medulla oblongata, pons, and midbrain

The reticular formation is what?

A netlike region of interspersed gray and white matter

Medulla oblongata:

Begins at the foramen magnum and extends to the pons

The medulla contains what?

Sensory and motor tracts between spinal cord and brain

Pons:

Connects parts of the brain and relays information from the cerebellum to the cerebrum

Midbrain:

Coordinates head, eye, and trunk movement in response to visual and auditory stimuli

Tectum:

The roof of the midbrain that receives sensory information

Tegmentum:

The floor of the midbrain that initiates motor output

Cerebellum:

Modifies and monitors, but does not initiate motor output

The cerebellum maintains what?

Equilibrium and balance

The cerebellum does what to motor actions?

Refines, smooths, and coordinates skeletal muscle contractions

Diencephalon:

Includes thalamus, hypothalamus, and epithalamus

Thalamus:

Processes sensory information and relays it to the cerebrum

Hypothalamus: (know!)

Controls and integrates autonomic nervous system activity

The hypothalamus also does what?

Controls body temperature and homeostasis

Epithalamus:

Contains the pineal gland and is involved in olfaction

The pineal gland secretes what?

Melatonin

Cerebrum:

Responsible for integration of complex sensory and neural functions and voluntary activity

Cerebral cortex:

The outer layer of gray matter of the cerebrum

Subcortical:

White matter underlying the cerebral cortex

Corpus callosum:

A broad band of white matter connecting the cerebral hemispheres