山东大学：《医学生理学 Medical Physiology》课程教学资源（PPT课件讲稿，人体生理学 Human Physiology）Chapter 10 Nervous System part 3 Function of the Nervous System

Part 3 Sensory function of the nervous System

Part 3 Sensory Function of the Nervous System

Sensory pathways o Sensory systems allow us to detect, analyze and respond to our environment ascending pathways o Carry information from sensory receptors to the brain o Conscious reach cerebral cortex o Unconscious do not reach cerebral cortex o Sensations from body reach the opposite side of the brain

I Sensory pathways ⚫ Sensory systems allow us to detect, analyze and respond to our environment ⚫ “ascending pathways” ⚫ Carry information from sensory receptors to the brain ⚫ Conscious: reach cerebral cortex ⚫ Unconscious: do not reach cerebral cortex ⚫ Sensations from body reach the opposite side of the brain

1. Sensory receptors A: Free nerve endings(pain, temperature) 060 A B: Pacinian corpuscle(pressure) C: Meissner's corpuscle(touch) B C D: Muscle spindle(stretch)

1. Sensory receptors A: Free nerve endings (pain, temperature) B: Pacinian corpuscle (pressure) C: Meissner’s corpuscle (touch) D: Muscle spindle (stretch) A B C D

Hairy skin Glabrous skin Merkels disk Epidermis Epidermal dermal border Free nerve ending Dermis Meissner corpuscle Hair follicle receptor Pacinian corpuscle Ruffini's ending Ruffini's endings respond to tension and stretch in the skin

Ruffini's endings respond to tension and stretch in the skin

2. Sensory pathways: 3 neurons o 1st: enters spinal cord from periphery o 2nd: crosses over(decussates ), ascends in spinal cord to thalamus o 3rd: projects to somatosensory cortex

2. Sensory pathways: 3 neurons ⚫ 1 st: enters spinal cord from periphery ⚫ 2 nd: crosses over (decussates), ascends in spinal cord to thalamus ⚫ 3 rd: projects to somatosensory cortex

2. 1 Spinothalamic pathway o Carries pain, temperature C touch and pressure signals 1 st neuron enters spinal cord through dorsal root 2nd neuron crosses over in spinal cord, ascends tO thalamus o 3rd neuron projects from thalamus to somatosensory cortex

2.1 Spinothalamic pathway ⚫ Carries pain, temperature, touch and pressure signals ⚫ 1 st neuron enters spinal cord through dorsal root ⚫ 2 nd neuron crosses over in spinal cord; ascends to thalamus ⚫ 3 rd neuron projects from thalamus to somatosensory cortex

Thalami Face Arm spinothalamic pathway Lee

spinothalamic pathway

Spinothalamic Pathway Primary somatosensory cortex (S1) Thalamus Medulla Small dorsal Dorsal Small sensory fil oot axons Spinothalamic tract Painl temperature some touch Spinal cord

Spinothalamic Pathway Small sensory fibres: Pain, temperature, some touch Primary somatosensory cortex (S1) Thalamus Medulla Spinal cord Spinothalamic tract

Spinothalamic damage Left spinothalamic pathway spinal cord injury L3 Loss of sense of Touch .Pain Warmth/cold n rignt leg

Spinothalamic damage spinothalamic pathway Left spinal cord injury Loss of sense of: •Touch •Pain •Warmth/cold in right leg

2.2 Dorsal column pathway o Carries fine touch. vibration and conscious proprioception signals o 1st neuron enters spinal cord through dorsal root ascends to medulla(brain stem) neuron crosses over in C medulla: ascends to thalamus δ处 ●3 neuron projects to 分z somatosensory cortex

2.2 Dorsal column pathway ⚫ Carries fine touch, vibration and conscious proprioception signals ⚫ 1 st neuron enters spinal cord through dorsal root; ascends to medulla (brain stem) ⚫ 2 nd neuron crosses over in medulla; ascends to thalamus ⚫ 3 rd neuron projects to somatosensory cortex