Sensory nerve : neuron that transmits impulses from a sensory receptor into the CNS,

Motor nerve : transmits impulses from CNS to an effector organ

Sensory nerve : - Receptors

- Nerve

- CNS

Potential receptors

Modality labeled line principles

SOMATIC SENSATIONThe somatic senses can be classified into three physiologic types :

(1) the mechanoreceptive somatic senses, which include both tactile and position sensations that are stimulated by mechanical displacement of some tissue of the body;(2) the thermoreceptive senses, which detect heat and cold; and (3) the pain sense, which is activated by any factor that damages the tissues

1. Dorsal column - medial lemniscal system

2. Anterolateral system :

Motor system in Spinal Cord Motor system in Brainstem Motor system in Basal Ganglia

MOTOR SYSTEM

MOTOR SYSTEM IN SPINAL CORD

The brain stem consists of the medulla, pons, and mesencephalon.

The brain stem is its own master because it provides many special control functions, such as the following:1. Control of respiration2. Control of the cardiovascular system3. Partial control of gastrointestinal function4. Control of many stereotyped movements of the body5. Control of equilibrium6. Control of eye movements

Finally, the brain stem serves as a way station for “command signals” from higher neural centers.

The reticular nuclei are divided into two major groups: (1) pontine reticular nuclei, located slightly posteriorly and laterally in the pons and extending into the mesencephalon, and (2) medullary reticular nuclei, which extend through the entire medulla, lying ventrally and medially near the midline.

These two sets of nuclei function mainly antagonistically to each other, with the pontine exciting the antigravity muscles and the medullary relaxing these same muscles.

The pontine reticular nuclei have a high degree of natural excitability. In addition, they receive strong excitatory signals from the vestibular nuclei, as well as from deep nuclei of the cerebellum

The medullary reticular nuclei transmit inhibitory signals to the same antigravity anterior motor neurons by way of a different tract, the medullary reticulospinal tract, located in the lateral column of the cord

The basal ganglia, like the cerebellum, constitute another accessory motor system that functions usually not by itself but in close association with the cerebral cortex and corticospinal motor control system. In fact, the basal ganglia receive most of their input signals from the cerebral cortex itself and also return almost all their output signals back to the cortex.

These ganglia consist of the caudate nucleus, putamen, globus pallidus, substantia nigra, and subthalamic nucleus. They are located mainly lateral to and surrounding the thalamus, occupying a large portion of the interior regions of both cerebral hemispheres.

The vestibular nuclei transmit strong excitatory signals to the antigravity muscles by way of the lateral and medial vestibulospinal tracts in the anterior columns of the spinal cord. Without this support of the vestibular nuclei, the pontine reticular system would lose much of its excitation of the axial antigravity muscles

The specific role of the vestibular nuclei, however, is to selectively control the excitatory signals to the different antigravity muscles to maintain equilibrium in response to signals from the vestibular apparatus.

Cognitive Control of Sequences ofMotor Patterns—The Caudate Circuit

Executing Patterns of Motor Activity—The Putamen Circuit

(1) dopamine pathways from the substantia nigra to the caudate nucleus and putamen,

(2)gamma-aminobutyric acid (GABA) pathways from the caudate nucleus and putamen to the globus pallidus and substantia nigra,

(3) acetylcholine pathways from the cortex to the caudate nucleus and putamen, and

(4) multiple general pathways from the brain stem that secrete norepinephrine, serotonin, enkephalin, and several other neurotransmitters in the basal ganglia as well as in other parts of the cerebrum.

Parkinson : decreased dopamine from subst nigrae

Huntington’s chorea : GABA decrease produced by caudatus & putamen

Athetosis : insufficiency in thalamicus nuclei ( lentikularis nuclei)

Hemiballismus : subthalamicus nuclei

CEREBELLUM

Vermis : control functions for muscle movements of the axial body, neck, shoulders, and hips

The intermediate zone of the hemisphere is concernedwith controlling muscle contractions in the distalportions of the upper and lower limbs, especially thehands and fingers and feet and toes.

The lateral zone of the hemisphere operates at amuch more remote level because this area joins with thecerebral cortex in the overall planning of sequential

motor movements.