The Nervous SystemThe Nervous System

Directions in the Nervous SystemDirections in the Nervous System

Anterior orRostral

Posterior or Caudal

Dorsal orSuperior

Ventral orInferior

Medial

Lateral

Slice and Dice: Planes of ViewSlice and Dice: Planes of View

Central and Peripheral Nervous Systems.Central and Peripheral Nervous Systems.

Divisions of the Nervous SystemDivisions of the Nervous SystemCNS - Division located within the skull and spinal cord.

PNS – Division located outside the skull and spine.

PNS Divisions: Somatic – interacts with external environment. Composed of afferent nerves from skin, muscles, eyes, ears, etc., to the CNS and efferent nerves from the CNS that carry signals to the skeletal muscles.Autonomic – regulates internal environment. Afferent nerves carry signals from internal organs to the CNS. Efferent nerves carry signals from the CNS to internal organs. Sympathetic = autonomic motor nerves projecting from the lumbar and thoracic regions of the spine. Parasympathetic = autonomic motor nerves projecting from the brain and sacral region of the spine.

Afferent – Towards the CNS.Efferent – Going away from the CNS.

The Autonomic Nervous SystemThe Autonomic Nervous System

The Cranial NervesThe Cranial NervesPeripheral Nerves Projecting Directly from the Brain.Peripheral Nerves Projecting Directly from the Brain.

Spinal CordSpinal CordGray Matter = cell bodies, unmyelinated axons. Dorsal and Ventral Horns are gray matter.

White Matter = myelinated axons

Spinal Nerves are attached to spinal cord at 31 different levels (62 spinal nerves).

Spinal Cord IISpinal Cord IIDorsal root axons are sensory unipolar neurons, with their cell bodies grouped just outside the spinal cord forming the dorsal root ganglion. Synaptic terminals are in dorsal horn.

Ventral Root Neurons are motor (efferent) multipolar neurons with their cell bodies in the ventral horn.

The Ventricles and Cerebral Spinal The Ventricles and Cerebral Spinal FluidFluid

Cerebral spinal fluid (CSF) is produced by the choroid plexus.Choroid plexus – networks of small vessels that protrude into the ventricle from the pia mater.Dural Sinuses – Large blood filled cavities that absorb excess CSF.

The Blood-Brain BarrierThe Blood-Brain BarrierImpedes passage of many toxic substances into the brain.

Caused by the tightly packed cells of the cerebral blood vessels. Astrocytes, a form of glial cell, further cover the walls of blood vessels to help maintain this dense packing.

Differentially allows access of certain substances (I.e. hormones) to particular parts of the brain.

Early Brain DevelopmentEarly Brain Development

Divisions of the Adult BrainDivisions of the Adult Brain

Myelencephalon and MetencephalonMyelencephalon and Metencephalon

Myelencephalon (also called the medulla) is composed largely of fiber tracts. The Reticular formation (little net) plays a role in arousal, attention, sleep and various cardiac, respiratory and circulatory reflexes.

Metencephalon: 2 Division (1) Pons (ascending and descending fiber tracks and part of reticular formation. (2) Cerebellum (little brain) is a sensorimotor structure controlling fine motor movements.

MesencephalonMesencephalon2 Divisions: (1) Tectum or “roof” which is composed of two bumps called colliculi (little hills). There is an superior and an inferior pair of colliculi. Vision.

(2) Tegmentum, ventral to the tectum, contains the RAF, fiber tracts, and the periaqueductal gray (pain and analgesia, especially opiates), the substantia nigra (sensorimotor), and the red nucleus (sensorimotor).

DiencephalonDiencephalon

Composed of the Thalamus and the Hypothalamus. The thalamus is the top of the brainstem, and the two lobes are joined by the massa intermedia. In between the lobes is the 3rd ventricle. Below lies the Hypothalamus, which exerts it’s effects by releasing hormones from the pituitary gland. (Pituitary actually means “snot”).

ThalamusThalamus

Most Thalamic nuclei project to the cortex. Some are sensory relay nuclei such as the lateral geniculate nucleus (visual), medial geniculate nuclei (auditory) and ventral posterior nuclei (somatosensory).

HypothalamusHypothalamus

Below (hypo) the thalamus: Regulates release of hormones from pituitary gland. On the ventral surface is the optic chiasm where the optic nerves from the eyes come together. Most decussate or cross over to the other hemisphere of the brain here, while others remain ipsilateral. The mammilary bodiesare also on the ventral surface and involved in swallowing and olfaction.

Telencephalon: Major FissuresTelencephalon: Major Fissures

Lobes of the brainLobes of the brain

Lobes and Important GyriLobes and Important Gyri

Layers of the CortexLayers of the Cortex

The Limbic SystemThe Limbic System

Limbic = ring (of subcortical structures).Regulation of motivated behaviors “the four F’s”Fleeing; Fighting; Feeding; and Sexual Behavior

Basal GangliaBasal Ganglia

Voluntary motor responses.Note the amygdala is considered part of both the limbic system and basal ganglia.

Types of NeuronsTypes of Neurons

The NeuronThe Neuron

The Cell MembraneThe Cell Membrane

The NeuronThe Neuron

Inside the NeuronInside the Neuron

The NeuronThe Neuron

MyelinationMyelination

Schwann Oligodendrocyte

AstrocytesAstrocytes