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continued from the  Brain Page of Nervous System


Neurons and Nerves
The Brain & Spinal Cord
Cranial Nerves
Peripheral Nervous System
Autonomic Nervous System
Senses: Eye diagrams, Hearing, Smell, Taste, Taste & Tongue Sensation, Balance
Memory , Memory types, Creation of Memory,
Higher Functions
Altered States


Taste (see location of the various components in Figure 09):

  • Papillae - The papillae are those small elevations visible to the naked eyes. There are three types of papillae located from the back of the tongue toward the tip. Filiform papillae are generally conical or pointed; fungiform papillae are flat-toped; vallate papillae are larger with an outer groove (see Figure 20). Many taste buds lie along the walls of the papillae. Isolated ones also are present on the palate, the pharynx, and the epiglottis. Sense of Taste
  • Taste buds - The tasting, or gustatory, cells in the buds have hairy tips which detect chemicals in solution (secreted by the gland at the bottom of papilla). When stimulated by flavor molecules, these cells generate nerve signals, which they send to the taste center on the brain's cortex, and also to the hypothalamus, which is concerned with appetite and the salivating reflex.
  • Taste nerve pathway - The nerve signals are carried by three nerves in each side of the tongue (cranial nerves) to a small part of the medulla (brain stem). The signals then travel to parts of the brain, such as the hypothalamus, the thalamus, and the gustatory part of the sensory cortex - the "taste center", where the signals are interpreted (Figure 21). The thalamus acts like a relay station, shunting the data onto appropriate cortical areas for processing. The sense of taste tells us what is good to eat. It evolved to pick out sweet, ripe fruits and energy-packed sugars
  • [view large image] and starches. Likewise, taste is is extremely sensitive to bitter flavors, because many poisonous berries, fruits and fungi are bitter-tasting.

    Sensations (see location of the various components in Figure 09):

  • Skin - Skin has a thin epidermis, which is mainly for protection, and a thicker dermis below. In addition to small blood vessels and sweat glands, it has tiny nerve endings in the various type of touch receptors (see Figure 09).
  • Receptors -
  • Proprioceptors - The sense of position and movement of limbs is dependent upon receptors termed proprioceptors (Figure 22a). They are located in the joints and associated ligaments and tendons that respond to stretching, pressure, and pain. Nerve endings from these receptors are integrated with those received from other types of receptors so that we know the position of body parts.
  • Sensory nerves - Nerve impulses may reach the somatosensory cortex for analysis before a response is decided. These result in voluntary actions - a deliberate response. Sometimes the stimulus require immediate action (such as from the burning sensation), a reflex action is taken without the conscious control of the brain. These are the involuntary actions directed by the spinal cord. We only become aware of them when other impulses are sent to the brain to "inform" what has happened. The path which impulses travel along during a reflex action is called a reflex arc. Not all the body parts
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