Functions of the Nervous System To carry out its normal role, the nervous system has three overlapping functions. Much like a sentry, it uses its millions of sensory receptors to monitor changes occurring both inside and outside the body; these changes are called stimuli, and the gathered information is called sensory input.
Reflex actions Of the many kinds of neural activity, there is one simple kind in which a stimulus leads to an immediate action. This is reflex activity.
By reflex, Hall meant the automatic response of a muscle or several muscles to a stimulus that excites an afferent nerve. The term is now used to describe an action that is an inborn central nervous system activity, not involving consciousnessin which a particular stimulus, by exciting an afferent nerve, produces a stereotypedimmediate response of muscle or gland.
The anatomical pathway of a reflex is called the reflex arc. It consists of an afferent or sensory nerve, usually one or more interneurons within the central nervous system, and an efferent motor, secretory, or secreto-motor nerve. Most reflexes have several synapses in the reflex arc.
The stretch reflex is exceptional in that, with no interneuron in the arc, it has only one synapse between the afferent nerve fibre and the motor neuron see below Movement: The regulation of muscular contraction. The flexor reflexwhich removes a limb from a noxious stimulus, has a minimum of two interneurons and three synapses.
Probably the best-known reflex is the pupillary light reflex. If a light is flashed near one eye, the pupils of both eyes contract. Light is the stimulus; impulses reach the brain via the optic nerve; and the response is conveyed to the pupillary musculature by autonomic nerves that supply the eye.
Another reflex involving the eye is known as the lacrimal reflex. When something irritates the conjunctiva or cornea of the eye, the lacrimal reflex causes nerve impulses to pass along the fifth cranial nerve trigeminal and reach the midbrain.
The efferent limb of this reflex arc is autonomic and mainly parasympathetic. These nerve fibres stimulate the lacrimal glands of the orbit, causing the outpouring of tears.
Other reflexes of the midbrain and medulla oblongata are the cough and sneeze reflexes. The cough reflex is caused by an irritant in the trachea and the sneeze reflex by one in the nose.
In both, the reflex response involves many muscles; this includes a temporary lapse of respiration in order to expel the irritant.
By seven and a half weeks after conceptionthe first reflex can be observed; stimulation around the mouth of the fetus causes the lips to be turned toward the stimulus.
By birth, sucking and swallowing reflexes are ready for use. Although the word stereotyped is used in the above definition, this does not mean that the reflex response is invariable and unchangeable. When a stimulus is repeated regularly, two changes occur in the reflex response—sensitization and habituation.
Sensitization is an increase in response; in general, it occurs during the first 10 to 20 responses.
Habituation is a decrease in response; it continues until, eventually, the response is extinguished. When the stimulus is irregularly repeated, habituation does not occur or is minimal. There are also long-term changes in reflexes, which may be seen in experimental spinal cord transections performed on kittens.
Repeated stimulation of the skin below the level of the lesion, such as rubbing the same area for 20 minutes every day, causes a change in latency the interval between the stimulus and the onset of response of certain reflexes, with diminution and finally extinction of the response.
Although this procedure takes several weeks, it shows that, with daily stimulation, one reflex response can be changed into another. Repeated activation of synapses increases their efficiencycausing a lasting change. When this repeated stimulation ceases, synaptic functions regress, and reflex responses return to their original form.
Although a reflex response is said to be rapid and immediate, some reflexes, called recruiting reflexes, can hardly be evoked by a single stimulus. Instead, they require increasing stimulation to induce a response.
The reflex contraction of the bladderfor example, requires an increasing amount of urine to stretch the muscle and to obtain muscular contraction. Reflexes can be altered by impulses from higher levels of the central nervous system.
For example, the cough reflex can be suppressed easily, and even the gag reflex the movements of incipient vomiting resulting from mechanical stimulation of the wall of the pharynx can be suppressed with training. The so-called conditioned reflexes are not reflexes at all but complicated acts of learned behaviour.
Salivation is one such conditioned reflex; it occurs only when a person is conscious of the presence of food or when one imagines food.Mar 30, · We follow up last week's tour of the central nervous system with a look at your peripheral nervous system, its afferent and efferent divisions, how it processes information, the reflex arc, and.
Advanced nervous system physiology. Health and medicine. Advanced nervous system physiology. Lessons. Functions of the nervous system. Muscle stretch reflex.
Autonomic nervous system. Upper motor neurons. Somatosensory tracts. Cerebral cortex. Neural cells and neurotransmitters. Learn reflex lab anatomy physiology with free interactive flashcards.
Choose from different sets of reflex lab anatomy physiology flashcards on Quizlet. Log in Sign up. Anatomy and Physiology Nervous System Test- Reflex Arc.
Receptor. Afferent pathway (sensory neuron). nervous system: The Nervous System and Reflexes In general, nerve function is dependent on both sensory and motor fibers, sensory stimulation evoking motor response.
Even the autonomic system is activated by sensory impulses from receptors in . A reflex arc is the pathway traveled by the nerve impulses during a reflex.
Most reflexes are spinal reflexes with pathways that traverse only the spinal cord. During a spinal reflex, information may be transmitted to the brain, but it is the spinal cord, not the brain, that is responsible for the integration of sensory information and a response transmitted to .
NERVOUS SYSTEM The nervous system consists of the brain, spinal cord, sensory organs, and all of the nerves that connect these organs with the rest of the body. Together, these organs are responsible for the control of the body and communication among its parts.
Reflex and Sensory Physiology. Lab # 4 Satta Charis Bemah.