Nervous Systems & Sensory Reception: Mechanoreceptors

Brain Divisions

1. Hindbrain - coordination of movements; balance

2. Midbrain - reflexes of ears and eyes

3. Forebrain - memory, association, sensory

Cerebrum

right and left cerebral hemispheres connect by a tract called the corpus callosum

Cerebral Cortex

• thin layer of neurons and glial cells covering the cerebrum

• seat of conscious sensations and voluntary muscular activity

• motor, sensory, associative

• Primary motor cortex (right side of brain) - motor control

• Primary Somatosensory cortex (left side of brain) - sensory

• Association cortex - surface of cerebral cortex for higher mental activities

Thalamus

primary site of sensory integrationHy

Hypothalamus

regulates body temperature, hunger, thirst, coordinated responses to internal stimuli and emotions

Peripheral Nervous System (PNS)

receives information from the environment, conveys it to the CNS and carries responses to effectors such as muscle cells

• somatic

• autonomic

Somatic Systems

stimulates muscles to contract; skeletal muscles are excited by release of ACh

Autonomic Systems

coordinated by the medulla oblongata and innervate involuntary effectors (smooth muscles, cardiac muscle, glands)

• sympathetic division

• parasympathetic division

Reflex

sudden involuntary movement of muscles

• produces rapid motor response to stimulus because sensory neurons pass its information to a motor neuron in the spinal cord without high-level processing

How Sensory Information is Conveyed

1. Stimulation - physical stimulus impinges on sensory neuron

2. Transduction - stimulus energy is transformed into graded potentials in dendrites of the neuron

3. Transmission - action potentials develop in axon of sensory neuron and conduct to the CNS along afferent nerve

4. Interpretation - brain creates sensory perception from electrochemical events produced from stimulation

Transduction

• sensory stimulus causes stimulus-gated ion channels to open or close

• large stimulus the larger depolarization

• action potential is produced along the sensory axons into the CNS

Mechanoreceptors

stimulated by physical or mechanical forces

• skin, sense of touch

Proprioceptors

muscle length and tension

• continual ‘sense’ of where they are in space and time

Baroreceptors

detect blood pressure

• respond to amount of force that blood exerts on the walls of the aorta and carotid arteries