Physiology chapter 6.2

metabolic requirements for the brain

• continuous blood supply

• high metabolic rate

• fully aerobic metabolism

• exclusively uses glucose as an energy substrate

• no glycogen deposits

Blood flow blockade

Ischemic stroke

Forebrain regions

• cerebrum

• diencephalon

  • thalamus

  • hypothalamus

  • epithalamus (pineal gland)

Hindbrain regions

• pons

• medulla oblongata

• cerebellum

regions that make up the brainstem

• midbrain

• hindbrain

5 lobes

• frontal

• parietal

• temporal

• occipital

• insula

2 relevant structures of the cerebrum

• pre central gyrus → primary motor cortex

• postcentral gyrus → primary somatosensory cortex

gray matter in the CNS

• short non-myelinated neurons and neuronal somas

• most of the neuron-neuron synapses occur here

white matter in the CNS

• mostly myelinated axons and some non-myelinated axons organized in tracts

• incoming and outgoing information is transported to and from different regions of the gray matter

Blood-brain barrier

• protective mechanism that isolates the brain from uncontrolled stimulus

What is circulating in the blood brain barrier

• hormones

• amino acids

• ions

how is the blood brain barrier formed

• tight junctions between the endothelial cells

• wrapped astrocyte end feet and pericytes

• basement membrane

• contain a bunch of enzymes that will destroy neurotransmitters

gray matter in the cerebral cortex and the neurons

• gray matter covers the surface of the cerebral hemisphere

• Neurons

  • pyramidal

  • stellate (non pyramidal)

pyramidal cells

• neuron that is part of the gray matter in the cerebral cortex

• the major output neurons of the cortex

• execute actions

stellate (non pyramidal) cells

• neutron that is part of the gray matter in the cerebral cortex

• receive sensory input and perform local processing

• generate integration

white matter in the cerebrum and the 3 tracts

• white matter is organized into three types of tracts

  • projection tracts

  • commissural tracts

  • association tracts

commissural tracts

• tract of the cerebral white matter

• cross from one hemisphere to the other

Association tract

• tract of the cerebral white matter

• connect different regions within the same hemisphere

projection tracts

• tract of the cerebral white matter

• connects higher and lower bran retegions

  • ex. cortex to spinal cord / brain stem

what is a tract?

bundles of axons

Basal nuclei and 3 structures it includes

• masses of gray matter deep within the cerebral white matter

• includes the caudate nucleus, putamen and globus pallidus

limbic system

• includes portions of gray and white matter in the frontal and temporal lobes and part of the thalamus and hypothalamus in the diencephalon

• controls function of emotions partially

the cerebral cortex participates in (5)

• perception

• generation of skilled movements

• reasoning

• learning

• memory

basal nuclei participate in (1)

• coordination of skeletal muscle activity

Limbic system participates in (3)

• generation of emotions

• emotional behavior and its correlation with basic vital functions

• some aspects of learning

structures of the diencephalon

• thalamus

• hypothalamus

• epithalamus

thalamus

• collection of several gray matter nuclei

• synaptic really for sensory pathways on their way to the cerebral cortex

thalamus participates in (2)

• control of skeletal muscle coordination

• awareness and cortical arousal

  • ex. light from the curtain opening in the morning

hypothalamus

• lies below the thalamus

• connects with the pituitary gland

hypothalamus participates in the regulation of (8)

• pituitary gland function

• water balance

• autonomic nervous system (sympathetic and parasympathetic)

• eating and drinking behavior

• reproductive system

• generates and regulates circadian rhythms

• body temperature

• emotional behavior

epithalamus

• small mass of tissue that includes the pineal gland

the epithalamus participates in (10

• control of circadian rhythms through the release of melatonin

Brainstem

• contains axons of neurons passing back and forth between the spinal cord, cerebrum, diencephalon and cerebellum

• contains the reticular formation with multiple nuclei that control several of the basic functions of the body

• contains nuclei that originate the cranial nerves III to XII

functional aspect of the brainstem (4)

• reflect control of cardiovascular and respiratory activity

• control of swallowing and vomiting

• filtering sensory information ascending to the cerebral cortex

• innervation of the muscles, glands, and sensory receptors of the head and many organs in the thoracic and abdominal cities via the cranial nerves

Cerebellum

• similar anatomy as the cerebrum

• superficial cerebellar cortex of grey matter

• internal white matter

• additional gray matter nuclei

cerebellum participates in (1)

• integration information from muscles, joints, skin, eyes, vestibular apparatus, viscera, cerebrum and diencephalon to coordinate posture and balance

spinal cord

• cylinder of nervous tissue that lines within the vertebral column

• extends from brainstem to first lumbar vertebra (L1) originates 31 pairs of spinal nerves

Cervical spinal nerves

C1 - C8

Thoracic spinal nerves

T1-T12

Lumbar spinal nerves

L1-L5

Sacral spinal nerves

S1-S5

Coccygeal spinal nerves

Co1

gray matter in the spinal cord

• contains neuron cell bodies, dendrites, and proximal sections of axons

• distributed in bilateral

  • posterior (dorsal) horns

  • anterior (ventral) horns

  • lateral horns (in some regions)

white matter in the spinal cord

• contains tracts of axons that transmit information

  • to higher centers in the CNS → ascending tracts

  • from higher centers in the CNS → descending tracts

  • pathways also transmit information between different levels of the spinal cord

Cranial nerves

• 12 pairs

• originate in the brain stem

  • except for the vagus they innervate the head and neck structures

• can carry sensory / motor information or both (mixed nerves)

• some play a central role in the parasympathetic division of the autonomic NS

cranial nerves that play a role in the ANS

• oculomotor

  • parasympathetic fibers taht innervate smooth muscles that constiric pupil and alter lens shape for near and far vision

• facial

  • parasympathetic innervation of the mucous glads in the nose, palate, and lacrimal and salivary glands

• glossopharyngeal

  • parasympathetic innervation of the parotid salivary gland

• vaus

  • parasympathetic innervation of the organs and glands of the thorax and abdomen

ventral (anterior) horns in spinal nerves

• some interneurons, mostly somas of somatic motor neurons

• control voluntary movement

lateral horns in the spinal nerves

• somas of sympathy autonomic motor neurons

  • just thoracic and lumbar

most spinal neurons receive signals from:

• upper centers in the brain

• dorsal horns directly or via interneurons → reflexes

ventral root of spinal nerves

• MOTOR

• tells organs what to do → info comes from neuron of interneuron

dorsal root of the spinal nerve

• SENSORY

• unipolar neurons

• somatic sensory neurons (from somatic receptors)

• visceral sensory neurons (from visceral receptors)

  • make synapses with motor neurons (directly or indirectly via interneurons) to trigger reflexes

• unipolar neuronal somas of both grouped in the dorsal root ganglion

ventral and dorsal roots join to form the spinal nerves which contain fibers of:

• sensory neurons → somatic and visceral

• motoro neurons → somatic and sympathetic

Autonomic nervous system (ANS)

• divided into sympathetic and parasympathetic branches that produce opposite effects

• innervate the smooth and cardiac muscles and the glands

• most organic receive dual innervation (blood vessels sympathetic innervation only)

• involuntary fine-tuning of the functions of the body internal organs

• uses two sequential motor neurons (preganglionic and postganglioinic) and a combination on of two neurotransmitters t reach its effectors

Sympathetic division