BIO 223 Exam 4

Dr. Cavanaugh

Sensation

Arriving information

Perception

Conscious awareness of a sensation

General senses describe our sensitivity to

Temperature, pain, touch, pressure, vibration, proprioception S

Special sense 

Olfactory, gustation, visio, equilibrium, hearing 

Sensory pathways

Series of neurons that relays sensory information from receptors to CNS

Sensory receptors

Specialized cells or cell processes that monitor specific conditions

Receptor specificity

Each receptor has a characteristic sensitivity

Receptive field 

Area monitored by a single receptor cell. The larger the receptive field, the more difficult it is to localize a stimulus

Transduction

Conversion of an arriving stimulus into an action potential by a sensory receptor

Adaptation

Reduction of receptor sensitivity in the presence of a constant stimulus

Peripheral adaptation in PNS

Decreased activity of receptor

Central adaptation in CNS 

Inhibition of nuclei along sensory pathway 

Tonic receptors 

Always active. Action potentials are generated at a frequency that reflects the background level of stimulation. When a stimulus increases or decreases, the rate of action potential generation changes accordingly

Slow adapting receptors

Show little perception

Pain receptors

Remind you of an injury along after damage has taken place

Phasic receptors

Normally inactive. Provide information about intensity and rate of change of a stimulus. Action potentials are generated only for a short time in response to a change in the conditions they are monitoring

Fast adapting receptors

Respond strongly at first but then activity decreases

Exteroceptors 

Provide information about external environment 

Proprioceptors 

Reports positions of skeletal muscles and joints 

Interoceptors 

Monitors visceral organs and functions 

Nociceptors

Pain receptors. Free nerve endings with large receptive fields. Are common in superficial portions of skin, joint capsules, periostea of bones and around walls of blood vessels

This sensory receptor is sensitive to temperature changes, mechanical damage, and dissolved chemicals

Nociceptors

Fast pain (prickling pain)

Sensation reach CNS quickly and often trigger somatic reflexes. Relayed to primary somatosensory cortex and thus receive conscious attention

Slow pain (burning and aching pain)

Sensations cause generalized activation of reticular formation and thalamus. You become aware of the pain but only have a general idea of the area affected

Thermoreceptors

Temperature receptors. Sensations are conducted along same pathways that carry pain sensations. Sent to reticular formation, thalamus, and (to a less extent) primary somatosensory cortex 

Free nerve endings located in dermis, skeletal muscles, liver and hypothalamus 

Thermoreceptors 

Mechanoreceptors

Detects physical conditions. Sensitive to physical stimuli that distort their plasma membranes. Membranes contain mechanically gated ion channels that open or close in response to stretching, compression, twisting, and other distortions of the membrane

3 classes of mechanoreceptors

Tactile receptors, Baroreceptors, Proprioceptors

Tactile receptors 

Provide sensations of touch, pressure, and vibration 

Fine touch and pressure receptors. (Tactile receptors)

Extremely sensitive, narrow receptive fields, and provide detailed information about source of stimulation.

Crude touch and pressure receptors (Tactile receptors) 

Large receptive fields. Provides poor localization. Give little information about stimulus

Baroreceptors 

Detect pressure changes in blood vessels and in digestive, respiratory, and urinary tracts. Monitors changes in pressure in an organ. Respond immediately to change in pressure, but adapt rapidly

Proprioceptors 

A somatic sensation. Monitors positions of joints and skeletal muscles. 

Muscle spindles 

Monitors skeletal muscle length. trigger stretch reflexes 

Golgi tendon organ 

At junction between skeletal muscles and its tendon. Monitors tension during muscle contraction 

Receptors in joint capsules 

Free nerve endings that detect pressure, tension, and movement at the joint 

Chemoreceptors 

Detects chemical concentration. Respond to water and lipid soluble substance that are dissolved in body fluids. Exhibit peripheral adaptations in seconds. 

Monitors pH, carbon dioxide, and oxygen levels in arterial blood at carotid bodies and aortic bodies 

Chemoreceptors 

Free nerve endings

Branching tips of sensory neurons that respond to touch, pressure, pain, and temperature

Root hair plexus

Made up of free nerve endings stimulated by hair movement

Tactile discs

Fine touch and pressure receptors sensitive to shape and texture

Bulbous corpuscle

Sensitive to pressure and distortion of the deep dermis

Tactile corpuscle

Sensitive to fine touch, pressure, and low-frequency vibrations

Lamellar corpuscle

Sensitive to deep pressure and high-frequency vibration

First order neuron

Sensory neuron that delivers sensations to CNS

Second order neuron 

Interneuron in spinal cord or brainstem that receives information from first order neuron. Crosses to opposite side of CNS (Decussation)

Third order neuron

Neuron in thalamus that must receive information from second order neuron. Only sensations that reach our awareness pass through thalamus. Axon of third order neuron synapses on neurons of primary somatosensory cortex 

Somatic motor pathways always involve at least which 2 motor neurons

Upper and lower motor neuron

Upper motor neuron

Cells body lies in a CNS processing center. Synapses lower motor neuron. Activity may facilitate or inhibit lower motor neuron 

Lower motor neuron

Cell body lies in a nucleus of brainstem or spinal cord. Only axon extends outside CNS. Innervates a single motor unit in a skeletal muscle. Activation triggers a contraction in innervated muscle. Damage eliminates voluntary and reflex control over innervated motor unit

Motor program

Movement require simultaneous firing of countless neurons as part of a selected group of actions. 

Execution of any motor program requires

Firing of neurons in motor association area, firing of upper motor neurons, input from basal nuclei, cerebellum, spinal cord, and multimodal association areas, firing of lower motor neurons in PNS 

Role of cerebral cortex

Majority of upper motor neurons that control complex movements reside in primary motor cortex and premotor and motor association area

Plan and initiate voluntary movement by selecting an appropriate motor program and coordinating sequence of skilled movements

Cerebral cortex

Inhibits motor neurons of thalamus until they receive excitatory input from cerebral cortex

Basal nuclei

Monitors ongoing movements and integrates information about contraction and relaxation of muscles, positions of joints, direction, force, and type of movement that is going to occur 

Cerebellum 

Determines motor error

Cerebellum

Motor error

Difference between intended movement and actual movement that is taking place

Motor learning

Corrections for motor error are added over time to motor program. More repetitions of specific action, more corrections for motor error added to program results in more fluid error free motions

Autonomic nervous system

Involuntary control of visceral effectors. Smooth muscle, glands, cardiac muscle, adipocytes.

Divisions of the ANS

Sympathetic and parasympathetic nervous systems

Hypothalamus

Contains integrative centers. Neurons comparable to upper motor neurons in SNS. Motor neurons of CNS synapse on visceral motor neurons in autonomic ganglia 

Preganglionic neurons

In brainstem and spinal cord

Preganglionic fibers

Axons of preganglionic neurons. After leaving CNS, they synapse on ganglionic neurons

Autonomic ganglia

Contains many ganglionic neurons that innervate visceral effectors

Postganglionic fibers

Axons of ganglionic neurons

Visceral motor nuclei in the brainstem and spinal cord are known as 

Preganglionic neurons 

Sympathetic division

Fight, flight, or freeze. Prepares the body to deal with emergencies. Increases alertness, metabolic rate, and muscular abilities

Sympathetic division (thoracolumbar division)

Short preganglionic fibers in thoracic and lumbar segments of spinal cord. Preganglionic neurons located between segments T1 and L2. Cell bodies in lateral horns. Axons enter anterior roots. Ganglionic neurons in ganglia near spinal cord. Long postganglionic fibers target organs

Parasympathetic division

Rest and digest. Conserves energy and maintains resting metabolic rate

General patterns of response to increased sympathetic activity 

Heightened mental alertness, Increased metabolic rate, Reduced digestive and urinary functions, Activation of energy reserves, Increased respiratory rate and dilation of respiratory pathways, Increase HR and BP, Activation of sweat glands 

General patterns of responses to increased parasympathetic activity 

Decreased metabolic rate, Decreased HR and BP, Increased secretion by salivary and digestive glands, Increased motility and blood flow in digestive tract, Stimulation of urination and defecation 

Ganglionic neurons synapses in these three locations

Sympathetic chain ganglia, Collateral ganglia, Adrenal medulla

Sympathetic chain ganglia 

On either side of vertebral column. One preganglionic fiber synapses on many ganglionic neurons. Each ganglion innervates a particular body organ or group of organs. 

Sympathetic chain ganglia control effectors in

Body wall, thoracic cavity, head, neck, limbs

Collateral ganglia

Anterior to vertebral bodies. Contain ganglionic neurons that innervate abdominopelvic tissues and viscera 

Adrenal medulla

Center of each adrenal gland. Modified sympathetic ganglion. Ganglionic neurons have very short axons. When stimulated, they release neurotransmitters into bloodstream. Functions as hormones to affect target cells throughout body

Which structures contains a modified sympathetic ganglion

Adrenal medulla

All preganglionic neurons release this neurotransmitter at synapse with ganglion neurons

Acetylcholine

Sympathetic stimulation of Norepinephrine on cardiac muscle cells

Ion channels open on cardiac muscle cells. Raises both rate and force of contraction. Amount of blood delivered to tissues and blood pressure both increase. Maintains homeostasis during increased physical activity 

Sympathetic stimulation of Norepinephrine on smooth muscle cells

Constriction of blood vessels serving digestive, urinary, and integumentary system. Dilation of bronchioles, Relaxation of smooth muscle of digestive tract, Dilation of pupils, Constriction of blood vessels serving most exocrine glands

Sympathetic stimulation of Norepinephrine on cellular metabolism 

During times of sympathetic activation, nearly all cells, especially skeletal muscle, require higher amount of ATP. 

Norepinephrine binds to receptors on adipocytes

Triggers breakdown of lipids and release fatty acids into bloodstream

Norepinephrine binds to receptors on liver cells

Triggers release of glucose from glycogen and synthesis of glucose from other resources

Norepinephrine binds to receptors on cells of pancreas

Triggers release of hormone glucagon. Increases blood glucose levels

Sympathetic stimulation on secretion of sweat glands

Sympathetic nervous system attempts to maintain body temperature homeostasis during periods of increased physical activity.

Neurotransmitter than increases sweat gland secretions

ACh

Effects of sympathetic stimulation - Adrenal medulla 

Modified sympathetic ganglion at center of each adrenal gland. Innervated by preganglionic fibers that synapse on cells that secrete epinephrine. 

Effects of sympathetic stimulation - Adrenal medulla with epi and norepi 

Bloodstream carries neurotransmitters throughout body, Causes changes in metabolic activities of different cells including cells not innervated by sympathetic postganglionic fibers. Each last much longer than those produced by direct sympathetic innervation. 

Effects of sympathetic stimulation on other cells

Enhances mental alertness by increasing neurons activity in association areas of cerebral cortex. Temporarily increases tension generated by skeletal muscle cells during a muscle contraction. Increases blood tendency to clot. Trigger contraction of arrector pili muscles. Causes ejaculation of semen via effects on smooth muscle cells of male reproductive ducts 

In the sympathetic division of the ANS, which neurotransmitters can be released at the postsynaptic membrane 

ACh, epinephrine and norepinephrine 

Parasympathetic division (craniosacral division)

Long preganglionic fibers in brainstem and sacral segments of spinal cord. Autonomic nuclei are in all parts of brainstem and lateral horns of S2-S4. Ganglionic neurons in peripheral ganglia within or adjacent to target organs. Short postganlinic fibers in or near target organs 

Which nerve is responsible for the parasympathetic innervation of the lungs, heart, stomach, liver, pancreas, and parts of the small and large intestine

Vagus nerve

Effects of parasympathetic division in eyes

Constriction of pupils and focusing on near objects

Effects of parasympathetic division in digestive system

Secretion by digestive glands

Effects of parasympathetic division in reproductive system

Changes associated with sexual arousal

Effects of parasympathetic division in digestive system

Stimulation and coordination of defecation

Effects of parasympathetic division in urinary system 

Contraction of urinary bladder during urination 

Effects of parasympathetic division in respiratory system

Constriction of respiratory passageways (Bronchioles)

Effects of parasympathetic division in cardiovascular system

Reduced HR and force of contraction